I put large diameter HEI (coil in cap, two piece shaft) in my 302 GMC. Followed a 12 Port News Sept 1984 article by Jake Firebach #219. Had to modify (file) the alum. shaft housing to look exactly like the original GMC distributor end to stop oil leaks. Also increased the HEI mechanical spark advance range from 14 (stock) to 24 engine degrees to really make the GMC go. My initial (600 rpm idle) advance is 12 deg and total advance is 38 degrees. It idles and accelerates great.
