Good Gas Cap for 67-68 Camaro?

[Northeast Rod Run]

I put a non-vented cap on my '69 Camaro.
Of course a '68 cap is exposed and the '69 cap is under the tag.
Now it doesn't leak.
BUT ! , it builds up pressure and I keep thinking this will cause a problem.
Like , blowing out some seals in the fuel system or something.
I even had a bad fuel leak last winter after the car sat a while because the fuel system built up pressure and it started to seap out of the fuel line up front. ( I had the carb disconnected at the time )
I smelled fuel and was like, " What the hell ? ! "
Anyway, I have to release the pressure off the fuel tank every time I stop. Just to be safe.

One time I "lost" the cap to my '69 so I bought a new cap. Once the hot weather came in, my car would always have a hard time starting if it sat for a while, but then if it sat a bit longer it would be fine. finally realized that I was getting vapor lock. It took me a while to put one and one together (I have a bad memory), but I finally realized that I replaced a vented cap with a non-vented one. Once I fixed that... no more hard starting. So I never mind smelling a slight bit of fuel anymore