71 Cheyenne starting issue

[65chevysub]

Good Morning all. I am helping a lady friend with her 71 Cheyenne with a 350, but cant get it to start. It ran for about a minute, then wouldn't crank, but the solenoid was working. Replaced the starter, and battery, and its still doing the same thing. Positive cable to the starter is getting real warm at the same time. Truck has sat for 3 months since it last ran. It has an HEI distributor, wires are good as well as the plugs. Lots of wiring in the engine compartment that I think goes to the AC(removed), but don't think it's anything for ignition since it ran for a minute. Any ideas what to look for?
Thanks everyone