I put an early HEI in my GMC 302. It took some work. I followed the steps in Tech Tips on this site. The biggest problem was the old GMC (and early Chevy engines) like 36 to 38 degrees max advance and the HEI is limited to about 20. I had to modify the advance weights to mimic the old advance curve. It performs great and starts like a new engine. I think HP was increased by 5% or so.
