77 c20 electrical issues.

[Troglodyte]

My recently acquired 77 c20 (454) is giving me headaches. When I first bought it, it wouldn't start. First thought was the starter because it wouldn't even try to turn over even while being jumped. After some tinkering we figured it wasn't the starter because it wouldn't take a charge. So we swapped the cables and she started. Solved right? Wrong. Next day same story. Wouldn't start, battery won't charge. So new battery maybe? Wrong. Bought a battery and when I connected the negative it sparked and something shorted and smoked behind the block. Not sure what and I don't want to connect it again to see.

Any thoughts? I can't figure out what was smoking or why.