If it were me, I would go with a 350. Run the 305 untill it runs no more, and have a 350 ready to drop in. If you have the TBI, then it should drop on. A new chip is needed but you would rechip it anyway. I just like the extra edge a 350 has to offer. Plenty in the boneyards awaiting an expert touch.
Waiting for the 305 to smoke, CC the heads, port match, find just the right parts. Make it perfect and ready to be fired up.