Well Blue, all small blocks are pretty much the same size . You can find alot of 350 engines and 350 transmissions out there. You just need engine mounts and a trans mount to install them. I would go with the 350 engine rather than the 305 because they usually have more power. It would be good to get the engine trans and rearend from the same vehicle. Youll also have to address the rear lugs if you get a rear with 5 lugs. Hope this gives you some ideas. Good luck!
