I think possibly the one on the GM box. That's the one I have on the 70 GSX Stage 1 and the 69 convertible.
I wonder if they changed depending on the factory? I know its not for a 70 but this is what Duane posted for his 69 Motion GS. This could be a Canadian cap since his car was originally built in Canada. lol
I'm not voting, it's the lowest cap in the first pic. That said, most of those caps are the same and will work. They are just different earlier or later versions of the same cap. But, that particular cap was unique to 70 cars out of Flint + Lansing. Possibly other GMAC plants used different caps. I'm not familiar with the cap Mike posted at all.
My early build (Sept. 69) GS455 has the one in the far right of first photo. I believe it's original.
My GS (late January of 70) has the same cap. I am actually using a 1972 Vented cap. I wanted to use that cap because of the high performance mechanical fuel pump I use (CV Products Pump). The vented cap allows air in, but not fuel vapor out. I figured I could use as much venting as I could get. I also have the two vents at the front passenger side of the tank.
