A couple of questions 3.1 hybrid

[GEN II JBODY]

First of all this is my first post here, LOVE this site! I am sorry if I posted in the wrong spot though? I have a 3.1mpfi 1990 cavalier z24 and a hm282. I know a lot about cars and engines in general but would like to learn more.
I am planning on a 3.1/ 3400 hybrid w/3500 plenum. My question is:
What would my approximate compression ratio be with stock pistons and 3400 top end? 8.9cr? 9.6cr? or somewhere in between? Next question: would I benefit with thinner head gaskets for a little extra cr? Was thinking about a 272 crane cam for fun and lots of tuning. Final question for the moment: will the 3500 exhaust manifolds work on the 3400 top end? I seem to remember something about the exhaust bolt pattern being different?

Thanks in advance for any and all help, btw(i have read all 136+ treads in pushrod performance and most in pushrod general)

Brian (GEN II JBODY)

[TiredGXP]

According to the CR calculator on this site, you'd be looking at about 9.4 compression ratio.

Thinner head gasket will probably give you too little quench.

[GEN II JBODY]

thanks for the help (TiredGXP)

[GEN II JBODY]

3500 manifolds will work in my car with some modification