1965 273 Heads

Polarbear;

If your going to rebuild the engine, look for a ratio of not more than 9.5-1. That would be a 93 octane useage.
If the engine is in good shape, a milling of the heads can make up the difference. Just go to 9.0-1 and you'll be good. In general, a point of compresion is worth about 3% on the dyno. So it is not really worth pushing the ratio if you don't have to.

On a camshaft, the rest of the cars specs should be known before making a selection. Things like wieght of the car and rear gear ratio as well as your intended useage of the car.

Everyday driveabilty, some spirted driving, alot of spirted driving, street strip, etc.....