If last night's opening round is any indication, the contest for Virginia's 8th Congressional District seat is going to be a battle between sluggers.

Rep. Herbert E. Harris II, the three-term Democratic incumbent, came out on radio station WMAL's "Campaign 80" call-in show to accuse Republican challenger Standford E. Parris of "a conflict of interest" because of his holdings of oil company stock.

When the often acrimonious and sarcastic exchange ended 55 minutes later, Parris's wife, Jane, predicted, "They are going to get into a fist fight before this [campaign] is over."

The two men, who last squared off in 1974 when Harris unseated Parris in the post-Watergate purge of many Republicans in Congress, agreed on one thing last night. As Parris put it, "Herb and I take differing views on most issues."

A third candidate in the race, Deborrah Frantz, wants to repeal all laws regulating marijuana. On other issues, the 25-year-old independent often sided with Harris, telling him after the show, "You're not half bad. If I could just get you to come around on a couple of issues . . ."

The verbal brawl between the two men was touched off when a caller asked moderate Ed Meyer to seek the candidates' views on the causes on inflation.

Harris, 54, took the initiative, saying that "Stan and I have a fundamental difference of opinion. Stan consistently voted to promote the interests of the oil companies" during his one term in the House (1973-74). Harris then accused Parris of having "a conflict of interest because of your hundreds of thousands of stock" in major all oil companies.

"You know that's not true, Herb," interrupted the 51-year-old Parris.

"Then how much do you have?" asked Harris.

"It's on the record, all you have to do is read it," said Parris, referring to a financial disclosure statement he has filed as part of the campaign.

But that didn't satisfy Harris. "Don't you know how much it is, Stan?" he asked. "Is it more than $100,000?"

"I guess it is," replied Parris.

"More than $150,000?" pressed Harris.

"Who cares?" shot back Parris. He added that he bought the stock after he left Congress, and "if elected. I'll put the stock into a blind trust."

But Harris wouldn't permit the debate to take a new direction, so Parris finally reeled off these figures: "300 shares of Texaco, 500 shares of Mobil, 400 to 500 shares of Phillips Petroleum. I'm certainly not a major stockholder," Parris concluded.

"You are in my book," countered Harris.

Parris then downgraded the value of his stock to $40,000 to $50,000, but said "whatever the value, it is not terribly important" to the issues of the campaign.

"Your President Carter said the impact of oil prices on inflation is only 2 to 3 percent. Where is the other 18 percent coming from Herb?" Parris answered for him. "Since you have been in Congress, Herb, you have voted for $250 billion in deficits" in the federal budget.

And so it went.

Every time Parris tried to saddle Harris with "your president," Harris retaliated about "your governor," referring to Virginia Gov. John N. Dalton for whom Parris worked as congressional liaison until he resigned this summer to enter the congressional race.

Although time ran out on the radio show, the differences between Harris and Parris didn't. At the end, they were still arguing, taking different sides on federal funds for abortion (Harris yes, Parris no) and other bellwethers of political philosphy.

"Watch this campaign," grinned Parris.