You can make changes to the timing curve with new springs, weights, and a (working) vacuum cannister yes. But it will take a lot of experimentation to dial it in where the motor perofrms best. As Denny suggested, the factory specs are a good place to start.

JMO, but I have always heard that the smog era cars (your monte) ran the timing way retarded for emissions purposes and subsequently ran like pigs. So in the end, you may not land right on top of what the factory specs say.

Good luck with it. What your doing is a lost art amongst many who prefer to "bolt-on" their power and tune it "close enough" versus having everything dialed in to perfection for max performance from the existing combo.

You'll be a better technician in the end.