Washington and Los Angeles, the clubs with two of the best records in the National Basketball Association this season, also are involved in a struggle for the honor of having the best mark in pro basketball during the 1970s.

With just a quarter of a season left in this decade, the Lakers hold a four-game lead over Washington and a three-game bulge over the fading Boston Celtics in the race for the '70s' No. 1 winning percentage.

A study by The Washington Post of won-lost trends in pro basketball over the past decade started with the 1969-70 season, when the Bill Russell years at Boston had ended, and concluded after every club had played 62 games in this current campaign.

The study, which included records compiled by four ex-ABA teams while they were in that league, revealed a continuation of a significant power shift within the NBA over the last part of the decade.

Of the top 10 teams with the best records in pro basketball over the last 9 3/4 years (including three ex-ABA squads) only four appear likely to make this season's playoffs.

Just three years ago, that number was as high as seven. But since then, Boston, New York and Chicago, three dominant squads in the early to mid-1970s, have fallen badly. This season, the three are among the six worst clubs in the league.

The study also showed that over the past six seasons, the team with the top regular-season records failed to go on to capture the NBA championship. Included among the teams which stumbled in the playoff are the powerhouse 1973 Boston Celtics, who won 68 games, and the 1975 Bullets, who won 60.

Not since 1972, when Los Angeles compiled a record 69 triumphs, has a franchise walked away with both regular-season and title honors. And those Lakers could rely on such superstars as Wilt Chamberlain, Jerry West and Gail Goodrich.

Unlike the 1960s, which was dominated by the Celtics' nine championship teams, the '70s has seen the arrival of equality in the NBA. Seven clubs have each won at least one title and just Boston and New York have taken more than one.

Nor has any franchise been able to win back-to-back titles. The last to pull off that feat was Boston with crowns in 1968 and 1969.Washington, which won last season, is trying for consecutive championships this season.

There has been talk of dynasties during the 1970s to replace the old Celtics, beginning with the Willis Reed-Walt Frazier-Earl Monroe Knicks and Kareem Abdul-Jabbar Milwaukee Bucks early in the decade and ending with the Bill Walton's Portland Trall Blazers last season.

But the Knicks grew old, Abdul-Jabber tired of Milwaukee after one crown and left for Los Angeles and Walton was hurt near the end of last year and has not played this season.

During these past 10 years, no club has been able to win even 60 percent of its games. Los Angeles, No. 1 on the winninng list, has a.595 percentage with Boston trailing at.591 and Washington at.590.

Only the Lakers and the Bullets have been able to produce consistently excellent teams throughout the decade. Los Angeles had a 46-36 record in 1970 and Washington 50-32; this season, the Bullets have had the top mark in the league since December and the Lakers have moved into contending position the last month.

Washington had one losing year (1972) but still managed to make the playoffs the first nine seasons of the decade, a feat no other teams can match.

Los Angeles suffered consecutive below-.500 campaigns in 1975 and 1976 but slowly rebuilt around Abdul-Jabbar. Now the Lakers are threatening to win their first title since that glorious 1972 season.

The Celtics, despite horrible records the past two years, have remained near the top during the decade on the strength of those brilliant John Havlicek-Dave Cowens squads that were competitive through 1976, when Boston won its last championship.

Of the top 10 teams in the listings as ranked by winning percentages, only three -- Washington, Los Angeles and San Antonio (ex-ABA) -- are having standout years this season. Denver is above.500 but the Nuggets, who won 48 games in 1978 and 50 in 1977, have been a major disappointment while struggling to catch Kansas City in the Midwest Division.

Otherwise, the remaining seven Top 10 teams include some of the league's worst this season. Chicago, Indiana, Boston and New York have been vying since October with New Orleans and Detroit to avoid finishing with the poorest mark in the NBA.

The 11th through 18th teams in the listings in contrast, will produce seven playoff representatives this year. They include such newly emerging powers as Seattle, Atlanta and Kansas City and revamped clubs such as Philadelphia, Phoenix and Houston.

Perhaps the major surprise of the list is San Diego, the relocated former Buffalo team. While at Buffalo, the 8-year-old franchise compiled the worst winning percentage in the NBA. But this year, its bid for a playoff spot has enabled it to knock New Orleans into the cellar position.

None of the league's recent expansion teams has fared well, overall, in the decade. Portland won a title in 1977 but still ranks No. 19 on the list. Cleveland and San Diego, both of which began in 1971, are 20th and 21st while New Orleans, which started in 1975, is 22nd.

Another oddity is the high placement of Indiana. The Pacers were an ABA powerhouse, winning three titles before moving to the NBA. Yet in the new league, the club has been a dismal failure, compiling a 67-67 record in two full season. But they still rank eighth on the list.

Another ABA member, San Antonio, has reversed Indiana's trend. The Spurs were mediocre in the old league 291-297 over the last seven years), yet have a 96-68 record in two NBA seasons. Last year, they won 52 games, third best in the league, and are in contention for the best record this time around.

Despite the mystique surrounding big men, overpowering centers have not had that much influence on the rankings. Chamberlain and Abdul-Jabbar have been cornerstones of Los Angeles' success and the lattr player also was the pivotman for Milwaukee's best teams. But Cowens, Wes Unseld (Washington), Dan Issel (Denver), Nate Thurmond (Golden State) and Bill Paultz (San Antonio) never have been listed among the league's dominant players, yet their clubs are all among the decade's Top Ten.