Gas Cap Issues

[DT1]

I'm having trouble with gas caps on the 71.
It has a vapor recovery canister so I really don't need a vented cap.
The problem is that I can't seem to find an OEM type cap that doesn't leak.
I've ordered and received at least three non vented caps from different internet suppliers but all of them leak when the tank is filled to more than 3/4. I've looked at the filler neck and it seems to be fine. I've even tried a vented cap and it leaked like crazy. Another thing I've noticed about every one of the caps I've ordered from LMC, Ecklers, Etc is that they have all arrived with some sort of dent in them (Only cosmetic, on the top). I can't help but think these companies are selling blemished caps because they're boxed new and shipped in yet another box but still, all have been dented on arrival. Anyone here have or had this same issue?