Overnight ratings in Nielsen's top 12 markets Sunday night gave the Super Bowl a 46.8 rating and a 70 percent audience share . . .

sw,-2 sk,2 ld,10 A year ago, overnights in just nine Nielsen cities for Super Bowl XIX yielded a 43.3 rating, which, when all the precincts were counted, rose to a 46.4 national rating . . .

On Channel 4 here, the Bears and Patriots (well, the Bears, anyway) averaged a 47.1 rating (which means about 700,000 of the area's 1.5 million TV homes were watching), while 67 percent of all the sets-in-use were tuned to the game on WRC . . .

But local NBC audiences began tapering off with the postgame show . . .

As the evening progressed, "Murder, She Wrote" on Channel 9 ate up a lot of the remaining viewership for WRC so that by 11 p.m., WDVM's late news pulled a 20 rating and a 40 share, compared with a 17.4/34 for WRC's news and a 7.9/15 for WJLA . . .

Incidentally, the late Sunday news on WRC marked the return to the air of anchor Jim Vance, looking great, due, in part, to a rigorous weight-lifting program he pursued while on leave . . .

Vance was originally scheduled to make his debut last night but he and station management decided an early run would help him get comfortable on the air again . . .

Ending weeks of speculation, top management at Capital Cities/ABC Inc. yesterday announced that Roone Arledge has been named group president of ABC News and Sports. He will continue as president of ABC News . . .

Meanwhile, Arledge named Dennis Swanson, who has been in charge of ABC's five owned TV stations, as president of ABC Sports . . . conducting the day-to-day business of the division, reporting to Arledge. Arledge will continue as executive producer of ABC's coverage of the 1988 Winter Olympics in Calgary and will continue to have "creative input" when the spirit moves him . . .

Arledge is also executive producer of the network's four-day coverage next July marking the debut of a refurbished Statue of Liberty . . .

Swanson's previous experience in sports has apparently been limited to sportscasting at the University of Illinois and at WMAQ, the NBC-owned station in Chicago, before he joined ABC in 1976 as an executive producer at KABC in L.A. . . .

Arledge said yesterday that doesn't worry him a bit. "Dennis is a sports nut. He's one of those guys who know all the sports statistics and he's always been interested in that area" . . .

Swanson has been on the fast track at ABC since he turned around the fortunes of ABC's owned-and-operated WLS in Chicago a couple of years back as vice president and general manager. That success earned him the O&O vice presidency he held until yesterday's announcement . . .

His promotion leaves the status of Sports senior vice president Jim Spence -- who has had day-to-day reponsibility for the most part since Sports president Arledge took on the dual role as News president in 1977 -- up in the air. But yesterday sources at ABC said that Arledge, Swanson and their top bosses want him to stay as senior veep . . .

"Jim's been a very valuable person," Arledge said yesterday . . .

Until yesterday (actually, details of Arledge's promotion were finalized last week) Arledge's position as president of two important divisions at a television network has always been an anomaly in big-time TV . . .

In 1960 he joined ABC Sports as a producer and rose to vice president in 1963. Five years later, as his innovative coverage of the Olympic Games, Wide World of Sports and football programming gave the third-place perennial what status it had, he was named president of the division . . .

That inventiveness prompted the network to make him president of the moribund News division in 1977, too. While he has never been able to pull the evening news program into serious contention with CBS, programs like "Nightline" and a much stronger news presence have justified the choice. This week, third-place "ABC World News Tonight with Peter Jennings" is not that far off the pace and is earning critical praise, despite ABC's low primetime standing . . .

Nevertheless, there were those in both News and Sports who felt Arledge often spread himself too thin, notably in 1984, when he brought off the national political campaigns and the Winter and Summer Olympics while also producing ABC's first ever Super Bowl on a weekend that culminated with the 1985 inaugural . . .

John B. Sias, president of ABC and executive vice president of Capital Cities/ABC Inc. since the merger earlier this month, said at the time of the merger that Arledge had informed the company of his desire to concentrate his energies on news . . .

"We supported this decision, but felt his creative overview in this sports area was important. Roone's expertise and genius in sports is unmatched in this business," Sias said yesterday . . .

In a statement yesterday, Arledge said that he had considered making the move for the past year, and one factor was the ABC-Capital Cities merger. "It seemed to me that the appropriate time for a change is now, as the newly merged company determined its senior management structure for the future" . . .

"I'm delighted," he later told a reporter. "I'll concentrate almost totally on news and be involved just enough in sports, which is fun. If the timing had been different, I'd have done it a year ago but with the merger in the offing we couldn't talk" . . .

He said the new management "feels that news is the most important part of the network-affiliate relationship. I'm not talking about a one-hour newscast, but I do hope to see expansion of the News division in the future" . . .

Arledge skipped a top management meeting in Phoenix this past weekend so he could deliver news of the changes to the Sports division in person yesterday . . .

And oh, yes. Probably effective this very weekend, viewers will no longer see "Executive Producer Roone Arledge" at the top of the credits for any and all ABC Sports presentations . . . At least until 1988 . . .

Also in the News

NBC's "Today" show is starting to stomp ABC's "Good Morning America" on a regular basis . . . For the week ending Jan. 17 "Today" had a 5.6 Nielsen rating and a 25 percent audience share, beating GMA by half a rating point (the margin was eight-tenths of a point the previous week) . . .

GMA had a 5.1/23 and "CBS Morning News" slipped to a 2.8/13, the latter's lowest weekly rating since September . . .

In the past eight weeks, "Today" has won six weeks outright and tied GMA for first once . . .

Senate offices yesterday began receiving the bulk of C-SPAN's 24-hour coverage on internal Channel 2 . . . a service that is still not available to the House side . . .

Neither the House nor the Senate receives C-SPAN's coverage of the House, as both get the raw footage from House producers direct . . .

Meanwhile, a vote on TV coverage of the Senate is now not expected until after the debate on Conrail later this session . . .

CBS Entertainment announced yesterday that "Dream West," the seven-hour mini-series starring Richard Chamberlain as "one of America's most remarkable adventurers, John Charles Fremont," will air for three nights starting Sunday, April 13 . . . It's based on David Nevin's bestselling historical novel . . .

Jennifer Steinhauser has joined Channel 5 as a writer/producer. She comes from WTOG in Tampa, Fla. . . .

And Finally

Friends of Steve and Carol Gendel will be saddened to learn of the death of their 17-year-old daughter Kathy Lewis Gendel in Los Angeles on January 17 . . .

Kathy suffered a fatal reaction to prescribed medication. The Gendels adopted her and another daughter after the death 10 years ago of the children's parents, Rod and Judith Weller Lewis of Charlottesville, Va., who were close friends of the Gendels' . . .

Gendel, now health editor at KCBS in Los Angeles, was formerly with WDVM here . . .

In lieu of flowers, the family requests that contributions be made to Vista del Mar Children's Services, 3200 Motor Ave., Los Angeles, Calif., 90034 . . .