Actual compression of a 68, 340?

The only to be sure is to measure your own and calculate it. It is medium hard, but is achievable with a graduated beaker, 1/4" plexiglass, vernier calipers, and axle grease once you remove the head from the engine.

I could describe how to do it if you are willing to go through it, It just takes a little while to explain. If you really want to know, post me back and I can explain how to do it and try to keep it simple and unconfusing. Also, you will need to measure the thickness of your original head gasket.