correct 1971 roadrunner gas cap

I see there are several 'NOS' gas caps on ebay. what one would be the most correct for my 71 roadrunner built in march? thanks!
-kevin

anyone??

I dont know how correct those 'NOS' caps are,
but here is what a true NOS Chrysler in the box cap for your car looks like.
Actually in this case it's an NOS 'on' the box cap
Hope this helps.

1971 had two caps, the early (flat) one is in the photo above. The late (after Dec '71) cap hangs over the filler tube about 1 1/4" it's much thicker when you lay them flat. The caps do not interchange, I bought one from the auto parts store for $6 about a year ago.

Sorry, it should read after Dec '70. The filler neck is different because the deep cap would just spin, & not catch hold of the nubs. The car is a November built '71 Satellite equipped with N95.

oh great, yet another mid year change.. my car was built in march 71. do you have a picture of the 'later' style one?? thanks!
-kevin

also, was this still a 2 pong cap or a 4 prong?

the filler neck itself stayed the same though didn't it?

Pretty sure, for the b-body, that mid-year gas cap and filler neck change was in Feb 72', for the 72' model year. The cap was redesigned with a safety catch, requiring a full 180 degrees of rotation to remove.
These are Stant branded caps, left; before Feb 72', right; after Feb 72'