Zora Arkus- Duntov's engineers started work on XP series prototype in 1969
According to wikipedia this one from photo: "The XP-895 was first shown in late 1973"
Is it good date?
Close enough as the car was first shown at the New York Show in 1973.
In fact the first XP-895 was designed as a possible Corvette replacement by the GM Styling Dept in 1971 as I understand it. It was built in steel and was powered by two 2-rotor Wankel rotary engines stuck together to make one 4-rotor engine producing about 420 bhp!
The puzzle car is not this one, however, as you have correctly identified it as the 2nd version built in aluminium 1972/3 by Reynolds Metals Co under commission by GM and powered by more conventional means, a 454 cu in Chevy V8.
Nice looking car and IMHO far better-looking than any of the later Corvettes, although GM were not yet ready for any of these new-fangled ideas like mid-engined cars and were pretty sure their customers weren't ready for one either.
Here are a couple more pics:
