[AZKen]

It makes no sense to rebuild a GMC 305 V6. Fixing semi small issues is OK. These motors have virtually no parts left, no one knows anything about them and they are, for the present, available for a low price from non believers. Find a donor, hear it run and/or do a compression test. Check the oil. Keep your old one for the bolt on parts.

An easier option
If you like the truck and not worried about if it has a GMC 305A V6, Drop in a SBC. A SBC is a GM product. Lighter, faster, HEI, parts galore. That wouldn't hurt anything. Gives you the chance for any trans, manual or automatic with OD. Everything fits everything. Don't obsess over a GMC 305 V6. The truck itself is very nice to own.
Change course, be happy.

P.S. I didn't search your posts, so I don't know why you are rebuilding it?????????????