Call it "parity," as Commissioner Pete Rozelle does; call it balance, or call it mediocrity in the National Football League after a mid-term examination of eight games played; there were developments to savor despite a marathon weekend including Sunday and Monday night games.

There were ties for first place in all three divisions of the American Conference. Five teams had .500 records going into the game last night between 4-3 Miami and the 1-6 New York Jets. The three teams behind Oakland and San Diego in the AFC West were all even at 4-4 -- Kansas City, Denver and Seattle.

After an 0-4 start, the Chiefs rallied nicely under the forbearance of Marv Levy and will be questing for their fifth straight victory on Sunday at Kansas City, against another team coached by a former assistant to George Allen -- the Baltimore Colts of Mike McCormack.

Levy, who coached the special teams for Allen, made a gut decision in that area when he chose to engage Nick Lowery, a gypsy placekicker, and let go Jan Stenerud after 13 seasons with the Chiefs. Lowery had tryouts with the Redskins, New England, New York Jets and Cincinnati Berngals before Levy took him on.

Lowery, a graduate of Washington's St. Albans School, now has made good on 11 of 12 field-goal attempts and his 40-yarder with 1 minute 14 seconds remaining defeated Detroit, 20-17, on Sunday. He kicked a 52-yarder earlier in the game, his third success over 50 yards this season. Only Toni Fritsch of Houston has a better field-goal percentage, with 13 successes in 14 attempts.

Kansas City finished with a 7-9 record in 1979 and quarterback Steve Fuller of Clemson, the Chiefs' second pick on the first round of the draft, ranked last among the passers in the AFC. Now, he rates No. 8 after eight games, completing nearly 60 percent of his throws (105 of 174) with seven touchdowns. He hit on 12 of 18 against the Lions, pasing for one touchdown and running for another.

Levy's patience with Fuller paid off after the offensive line recovered from an assortment of injuries. The Chiefs will be catching the Colts after injuries among Bert Jones' blockers resulted in his being sacked 12 times on Sunday by the St. Louis Cardinals. It was especially embarrassing for McCormack because he is a former offensive lineman and line coach.

Coach O. A. (Bum) Phillips of Houston already has justified his trade for tight end Dave Casper of Oakland as the Oilers joined the Cleveland Browns atop the AFC Central at 5-3.

Phillips obtained Casper to pair with Mike Barber in a double tight end formation to take advantage of Earl Campbell's running. The Oilers used the formation about 90 percent of the time on Sunday in a 23-3 victory over Cincinnati and Campbell went 55 and three yards for touchdowns in rolling up 202 yards in 27 carries.

In Denver this Sunday he can become the first NFL runner to top 200 yards rushing in three straight games. He ran for 203 against Tampa Bay a week ago, when Casper joined the team. Thus, Campbell has gained 405 yards since the Oilers gave up a No. 1 and two No. 2 draft choices to the Raiders for Casper.

O. J. Simpson topped 200 yards in successive games twice, in 1973 and 1976.

After five games, Campbell ranked 13th among AFC rushers, handicapped by injuries that caused him to miss one game. Now he is No. 1, with 807 yards for eight games.

While Oakland and Cleveland were winning their third straight games, Pittsburgh was losing its third in a row with Cliff Stoudt starting at quarterback for the first time and Terry Bradshaw missing a start for the first time in 63 games, because of a jammed thumb on his throwing hand.

The Steelers also were playing without Lynn Swann, John Stallworth, Franco Harris and Jack Lambert because of injuries. The defending Super Bowl champions play at home against Green Bay on Sunday and will be solid favorites.

New England had the longest winning stretch snapped at five games in wind in Buffalo that gusted up to 40 mph. Steve Grogan of the Patriots had four passes intercepted while completing only 13 of 29; the Bills' Joe Ferguson had two passes picked off while hitting on only 12 of 28. It was note-worthy that all the points were scored with the wind at the backs of the offensive teams.