My first thought was that you have it 180 degrees out,, because that certainly causes popping and the no run situation. If you were able to swap distributors without moving anything, than you probably have a problem with your Pro Comp distributor. A couple of years ago one of the guys at Chet Herbert told me about 50% of the Pro Comp distributors came back. That was in a discussion where I was telling him that we bought two for a dirt track car that I build engines for, one was bad out of the box, and the 2nd had only 1/2 a roll pin through the gear, since the hole did not line up properly.
Reading your post again, you state that firing order was counter clockwise, that is not correct. Starting with #1, you put the wires clockwise on the cap (viewed from top)
