Help me with my electrical gremlins

[birdistheword]

So I just bought a 69 C10 that had been sitting in a barn for the last few years. filled the carb up with gas and it starts up and runs. But the starter cranks slow and might have a weird knock to it. But you can barely hear the engine run. After driving the truck a few miles the battery cable terminals on the battery are almost hot. The negative is warm but the positive is almost hot. The truck has some after market quick release cables but would it be the starter just being 1,000 years old? Almost everything is original on the truck. hanks for any suggestions or help. I was thinking about just getting a new starter and battery cables when I do an engine swap.