Is that a USAC race? It looks like Milwaukee.
Yes...at the time, the cars were interchangeable between the two series and Penske wanted to shake the car down after what happened at it's NASCAR debut in Charlotte at the end of May, 1972 for the World 600 where he finished 31st.
The car was taken back to the Penske shop in Michigan and completely rebuilt by the end of July, then entered in the USAC Pocono race on July 30th of '72. Where it finished 4th, which is way above expectations, but unfortunately the race was not a real test. Dave was 6 laps down and Richard Petty finished 22nd. Only 16 cars were still running out of the forty or so that started.
So Penske entered the car at Milwaukee for the USAC race on August 17th, 1972...where Dave finished 5th, three days later Penske ran it in the NASCAR race at Michigan where Dave finished 9th....this is the race where Bobby Allison finished 2nd, where he famously said, "where the hell did that Rambler come from?".
It was entered again two weeks later at the Darlington NASCAR race where Dave finished 7th....Bobby Allison won, but again commented on "that Rambler"
According to Bobby, what was impressive is that most of the rest of the cars still ran the big blocks and the small blocks did not have same weight advantage as they would starting in '73. 1973 was the watershed year for NASCAR as a transitional year for the small blocks. If I am not mistaken, that was the number one year of engine detonations in NASCAR history. Penske kept bringing the Rambler out of storage to fill the gaps due to his fleet getting decimated from blown engines.
Unfortunately, the Rambler was also known as the "flying brick" in that configuration....that all changed in '74 when they re bodied the Rambler into the sleeker Matador...Bobby Allison debuted the newer version at the Firecracker 400 in Daytona for the 1974 4th of July race....Bobby shocked the racing world, started 2nd, led the most laps and was in fact running away with the race until a late unexpected pit stop relegated him to 5th place one lap down (he was two laps down after the pit stop).
Bobby would take that Matador to multiple victories over the next few years. When Penske parked it (saying it was out of date) after the '75 season...Allison acquired it. When Bobby left Penske after the '76 season....Bobby dragged the old Matador out of the back forty and put it back on the track.
The last race that Bobby ran it was in 1980...probably hopelessly out of date, but it still finished 2nd at Michigan. The 8 year old chassis was pretty much out of date and engine parts were few and far between...but as the saying goes..."I'm not as good as I once was, but good once as I ever was".