according to TGO, the vortec base isn't a very good casting. It needs substantial clean up with a rotary tool. This isnt a bad thing necessarily, however buddies tend to drink lots of beer and watch you bust knuckles.
The TPI base flows plenty for a 305. What about a set of 58cc TFS heads and port match?
Your buddy needs to give you a price, a goal and '***** or get off the pot.'
I think the LT1 is an interesting proposition. I think the motor was 800, the harness and ecm was 2 or 300 and the crossmember was 300. Throw the hot-cam in there, a little prom flashing; notch the crossmember or use the LT1 Fbod one and the body harness should cover most of it. Redline is probably 6500, 350hp or more and latemodel dependability. I do not know if you'd have to modify the fuel system, but I do know the 4th gen and 3rd gen use a lot of the same 'tub' so most parts fit easily.
This is probably an easier swap than an LS however, there's more room to grow with an LS obviously.
Footnote; the LT heads were the basis for the vortecs.