Dan Ripley and Billy Olson shared the American pole-vault record of 18 feet 9 1/4 inches and the TAC/USA title tonight after a marathon competition that left both too tired to enter the prescribed jumpoff.

That was one of many harrowing finishes as 22 titles were decided on the final day. In perhaps the toughest and disappointing, John Gregorek was overhauled by Henry Marsh in the last few strides of the 3,000-meter steeplechase, maintaining Marsh's record of never losing to the recent Georgetown graduate.

The longest races produced two of the closest finishes. Craig Virgin, rebounding from a kidney ailment, ran down Steve Ortiz in the last few strides of the 10,000 meters and Francie Larrieu at 29 won her ninth national title by outkicking old rival Jan Merrill in the stretch of the 3,000.

Dave McKenzie spoiled a storybook finish in the hammer with a three-inch victory over Ed Burke, 42, whose 234-11 effort was his best since 1968. The discus was almost as close, as Cuban Luis Delis came from behind with a 225-5 effort to beat Mac Wilkins' 223-9.

Steve Scott ran away from Sydney Maree on the last lap to set a meet record of 3:34.92 in the 1,500 meters. Meet records were established in three women's events--Mary Decker Tabb, 4:03.37 for the 1,500; Denean Howard, 50.87 for the 400, and Merlene Ottey, 22.17 for the 200.

James Robinson won his fifth straight 800-meter title in 1:46.12, bouncing through puddles after a water truck had cooled off a track scorched by Cliff Wiley's 45.05 in a successful defense of his 400-meter crown.

Canadian Milt Ottey won the high jump at 7-5 3/4 as six other jumpers cleared 7-4 1/2. Navy's Leo Williams, over 7-4 1/2 on his third attempt, was officially placed fifth.

Eight men sailed 18-1 1/2 or better in the pole vault and it appeared that Dave Volz was going to win when he topped 18-5 1/4 on his first attempt. Ripley and Olson, however, had other ideas.

Ripley banged the bar on his second try at 18-9 1/4, but it stayed on the standard for an American mark. Olson, who set the expired record of 18-8 3/4 in March, could see a national team berth disappearing, too, as he tried to match Ripley.

Olson had passed after a single miss at 18-1 1/2, then dislodged the bar with his arm after a good assault on 18-5 1/4. His form was not as smooth on that final desperate try, but he cleared it without a touch.

Ripley and Olson each made three attempts at a world record of 19-1, then agreed to share first place rather than begin a jumpoff, which called for one more try at 19-1 and then a shift downward until a decision could be reached.

"We were both tired and on our way down, and at that point we had nothing to look forward to but getting hurt," said Olson, 23, who holds the world indoor best of 18-10. "I was really huffing and puffing after the record jump. It really wasn't as good a plant or as good a run as the one I missed before it, but I got over and in a deep pressure situation that's all you can ask."

"I was tired--I'd had more jumps than Billy and I'm older," said Ripley, 28. "I was already really happy after the American record and I'm afraid I had trouble staying psyched up. I had the record first--he tied me."

Both Olson and Ripley are hoping that the man who holds the world record of 19 feet 3/4 inch, Vladimir Polyakov, will be named to the Soviet team for the dual meet at Indianapolis July 2-3.

Marsh, America's top-rated steeplechaser, was 11th at the halfway point with Gregorek close behind pace-setting Randy Jackson. Gregorek moved in front with 3 1/2 laps to go and stayed there until Marsh struggled past in the stretch, to win in 8:22.94.

"I thought I had him tonight," Gregorek said. "I knew he'd be there, but I thought I had the jump on him. I'm gaining on him every time."