Need help with a knocking 305

[Off Road Red]

Okay so I went a bought an 85 Chevy half ton with a 305 in it, I knew that the motor needed work when I bought it, and here's what it's doing. It has a bit of a miss at idle, turns into a bad knock when you put your foot into it, but then runs smooth when your highway cruising.  I haven't had time to take it to a garage yet but we did a compression test on it and it's pretty well level all the way across, and the oil pressure is good. Some people think it's the camshaft, some think it's the ignition timing, or ignition related. What do you guys think could be wrong? The truck has about 70,000 original miles on it.