305 eats electrical parts?
 

My dad always complains about how (what is now my) our 1980 C10 with a 305 goes through distributor caps so badly. He said since he bought it new in 1980 every few years the distributor cap goes sour. They short out and burn a hole clear through the cap, and in the process taking plug wires and plugs with it. We tried several different brands and high quality caps but they all go bad. And my plug wires go bad, too. I have to replace my plug wires and probably plugs this weekend because one or more are shorting off on the block. Is the 305 the only block that does this or do all GM motors of the time period do this?

It sounds like you might not have a good ground for the engine do you have a ground strap going from the engine to the firewall. also you might need to rebuild the dist have you tried a new coil yet.?