Virginia ventured into the land of the giants tonight armed with nothing but a bag of slingshots but made every shot count in the second half to slay Minnesota, 58-55, to win the 43rd National Invitation Tournament at Madison Square Garden.

The Cavaliers, in completing a 24-10 season, were hopelessly outmanned up front but hung tough on the boards and refused to be intimated by the Big Ten school. Star guard Jeff Lamp was held in check and Ralph Sampson was not enjoying his usual success underneath, but Virginia received excellent efforts from Lee Raker and Mike Owens.

The forwards rescued the Cavs in the first half and also played well after intermission. The two made significant contributions both on the scoreboard and under the boards where the tall Golden Gophers waged a 40-minute war.

Raker and Sampson each scored five points to help UVA break away from the 29-29 halftime into a 44-38 lead with 9:07 to play in the game.

Virginia seemed to be hanging on for dear life until Lamp got rid of his nemesis, 6-foot-5 Trent Tucker. Even Lamp breathed a sigh of relief when Tucker drew his fifth personal foul with 6:05 to go and UVA clinging to a 48-45 lead.

Minnesota (21-11) then put its 6-11 star Kevin McHale on Lamp. Mistake. Seconds later Lamp launched his only successful long jump shot, in McHale's face, to maintain Virginia's three-point lead with 4:46 to play. Lamp finished with nine points.

"Lamp has to be denied the ball all the time," said Tucker. "He doesn't have good foot speed so you can do that. You know what kind of shots he wants on the court. I played him very physical. That's the way I'm used to playing."

Any team wth treetop range will almost surely get its share of opportunities underneath, and the Gophers scratched their way back on the shooting of Darryl Mitchell. Mitchell's two free throws, part of his 18-point output, put the Gophers up, 53-52, with 2:02 on the clock.

Sampson, named the tournament MVP and all-tourney along with Lamp, regained the lead with a pair from the line.

Next came the play both coaches considered one of the game's most most important. After calling a timeout, the Gophers tried to go inside but McHale's pass intended for Randy Breuer was tipped by Raker and picked off by Jeff Jones with 0:53 showing.

Terry Gates missed a chance to put Virginia ahead by three when he botched the front free throw of a one-and-bonus with 29 seconds left, but Sampson, who totaled 15 points and 15 rebounds, collared the ball and UVA spread out its offense again.

"My job is to get the ball," said Sampson. "Out defense turned the game around."

Lamp was quickly fouled and sank both shots to pad the lead to three points at 0:19, then Sampson made another big contribution.

McHale, who scored only eight points, nine below his average, went strong to the hoop but found his shot stuffed back at him by the 7-foot-4 freshman, Sampson was called for a foul and the Minnesota bench erupted, yelling for a goaltending call besides.

"It could have been goaltending. Both went up at the same time and the rim was shaking," said Jim Dutcher, the Minnesota coach.

McHale made both shots at 0:11 to cut the gap to 56-55. But the Gophers for some reason didn't foul as Virginia held the ball unitl Lamp was grabbed with two seconds left. He made both shots and Minnesota was dead.

Others selected all-tournament were Minnesota's Randy Brever and Mitchell and Illinoise Eddie Johnson.