im in need of either a small block chevy 350 or any size big block i have a stock 305 in my 1980montecarlo right now and it dont have enought power so im lookin for a good motor to bore and build up

Buy a crate Gm engine

look for a chevy or gm school bus or may be a c50 or 60 truck some of them had 350 and they have steel cranks and big valves. makes a good starting point.