Did you check the compression in that hole? Yes, try another plug.
Time on the side of the road has helped form my feelings about aftermarket HEI. When I ran it in my '53 pickup there was always a spare module in the glove box and a complete points distributer under the seat. Is the height on the other engine aftermarket or GM? I think there were two GM HEI distributers a small one & a big one. The big one is best but ugly.
