The Dallas Mavericks and Detroit Pistons now are prepared to offer between $750,000 and $1 million a year to lure Virginia's Ralph Sampson to the Natinal Basketball Association, a sum that would make his the highest the National Basketball Association, a sum that would make his the highest and rookie in league history.

"Our owners have said they will spend whatever it takes to sign him," said Jack McCloskey, the general manager of the Pistons.

"If he's not worth it, who is?" Dallas Coach Dick Motta said of the 7-foot-4 sophomore center who led the Cavaliers to the national semifinals of the NCAA tournament this season.

The Boston Celtics' Larry Bird earned between $600,000 and $650,000 his first season, the present record for a rookie.

Dallas and Detroit were the two worst teams in the NBA this season and are to flip a coin early next month to determine which will be able to chose Sampson in the June draft. As an undergraduate, Sampson must declare by April 25 if he will turn professional or return to school.

Under NBA rules, both Dallas and Detroit are permitted to make offers to Sampson as long as he doesn't employ an agent. He hasn't.

Dallas team owner Don Carter and Detroit's William Davidson have been convinced by their general managers and coaches to open their pocket books, all the way. And both clubs are trying to sell the vittues of their franchises and their cities to Sampson.

The Mavericks are in the process of preparing a videotape presentation featuring Motta, Carter and General Manager Norm Sonju talking about the franchise, its upcoming draft choices, the arena, the Dallas community and why the state of Texas is probably the only place the 7-4 Sampson can stretch out and be himself.

The Pistons lack that flair for showmanship. Instead, they are presenting a standard written report detailing the merits of their franchise and the attractions of Pontiac, Mich., and the Detroit area.

Among the things Sampson requested from the two teams was a detailing of their future plans: how they plan to obtain good players to go along with him and what their draft situation is.

Both teams are well-stocked with draft choices. Detroit will have either the first or second pick and the 13th pick in the first round this year. The Pistons have their own choice and Washington's first-round pick next year.

Dallas is even better off. The Mavericks have the first or second pick and the ninth pick in the first round this year, their No. 1 next year, their No. 1 and Atlanta's No. 1 in 1983, their No. 1 and Cleveland's in 1984 and their No. 1 and the No. 1s of Denver and Cleveland in 1985. That's 10 first-round choices.

The NBA's board of governors is to vote today on a proposal initiated by Sonju and McCloskey that would move up the Dallas-Detroit coin flip to sometime before April 25. That proposal needs the approval of 18 of the league's 23 owners.

League sources indicated the proposal probably will fail, which means Sampson would have to make a decision before knowing which team he could end up with.

Sampson, meanwhile, hasn't given any indication of the direction in which he is leaning.

Virgnia Coach Terry Holland, who had some anxious moments two years ago when Sampson was selecting a college, is just as anxious now, wondering if he can hold onto his star for at least one more season.

Because Sampson cannot employ an agent and has said he doesn't want any first-hand contact with any pro team, Holland has volunteered to serve as the middleman.

"I have no qualms with any of this, because I promised Ralph when he came to Virginia that I'd do it this way," Holland said. "The main thing I want Ralph to do is make the right decision. I can live without him better than I can live with him is he stays, but has second thoughts about it. b

"Nobody is completely pure in this thing, not even me. Ralph just has to recognize that hat everybody wears and understand why they are saying what they're saying."

Most NBAscouts feel Sampson is a player to build a franchise around, but that he is still a year or so away from being able to dominate the pro game.

"He just isn't that strong yet," said Bullet General Manager Bob Ferry.

"But he'll fill out."