+1 @ Jeff73Mach1
Automatic = Flexplate & Manual = Flywheel
6 Cyl = 0 oz bal
8 Cyl = 28 oz balance until later in early 80s then 50 oz
You may need to replace the flexplate if the teeth are eaten up. Replacing a flexplate is NOT easy, you need to at least pull the engine from the tranny (can be 2-3 inches apart) and unbolt it. I did it about 3 months ago and it took 3-4 hrs. Make sure you torque the bolts to the right spec. I did it on a 289 but a 302 should is the same...not sure about the bigger engines though. I have a 157 tooth flexplate ($60) with 28 oz balance on a C4. The other flavor (162T I think) is bigger so it won't fit in your tranny housing. The flexplates should only fit on 1 way (5 bolt holes) so replacing it isn't rocket science. If you have the tools (engine hoist) I'd go with that if you are sure the starters aren't the problem.
You'll need to match up the flexplate with your trans and engine. I googled it so it wasn't hard to figure out.