Re: trouble starting
Sounds like it may be the starter solenoid failing when it heats up. When I replaced the starter in my '73 Scout II w/ 304 V8, the starter and solenoid came together. It was cheap but it took two tries to get a good working rebuilt starter. If I had it to do over again I would have put a Delco Remy Starter/solenoid in there. But the second of the cheaper units ($59 as opposed to $89 for Delco) I put in is working fine so far.
There is a procedure on at least a couple of web sites for adding a GM front wheel drive or other starter solenoid in a remote location away from the exhaust manifold. This could do the trick for you, assuming that's the problem.
You might try buying a can of "Circuit Cooler" spray from an electronics store like Radio Shack. After the starter begins acting up, turn the key off and get out and douse the starter solenoid real good with the circuit cooler spray for about 15 seconds. This stuff doesn't conduct and won't hurt anything to spray it on liberally. Cool the solenoide down as much as you can. You may see some frost develop for a moment while you're spraying which will condense rather quickly. This is not a problem. Anyway, after cooling off the solenoid turn the key and give it a try. If the starter/solenoid works after you've cooled it off, then you pretty much know with certainty at that point that the solenoid is bad.