I'd go with 9:1, unless decent gas is a problem in your area. "How to Hotrod Big Block Chevys" from HP books is a good place to start.

A 1974-vintage motor was built as a 'smog' motor; i.e. very low compression and not much cam. It'll have big combustion chambers, so you'll need at least flat-top pistons and maybe even a slight bump on them. I'd run factory cast-iron headers, if it was me. They're quiet, durable, and you should be able to find a set cheap at a swap meet.

As for a cam, get some name-brand one that's designed for pulling/RV use in non-emissions motors. It should be enough cam to make HP, but not so much as to kill low-end power.

Good luck!
George