Did you buy the engine to use in something? There is no way your going to bore a 305 3.73 inch bore size to even almost a 350 4.0 inch bore size. Even if you went .080 over you only getting to 3.81.
What you do have is good start, roller block, TBI heads are not bad. The engine uses a 350 crank and rods......so if you have 350 with a bad bottom end then there you go.
If you need the long block check the heads and see what you have, make sure they are in good shape and not cracked. Mill them for little more compression and use thinner head gasket. Besure to check your intake against the block and the heads to make sure it's going to seal correclty at the bottom of the intake (valley side) of the ports.
Get yourself a decent cam from Comp or anyone else. Use dual pattern, maybe look at some OEM grinds from a Z/28 or IROC if you want something cheaper.
Polish the heads combustion chambers and remove the sharp edges from the quench side of the chamber to the chamber. Do some minor clean up around the intake and exuahst valves, just cleaning up casting slag and making the flow areas/bends smoother.
Most of this is work you do yourself or get done fairly cheap. You will end up having 305 that will run pretty well and be in the thing CHEAP!! Heck you even change pistons if they dished to flat tops and bump the compression and not mess witht head milling at all, just depends on what your willing to spend. A 305 is not a bad engine, it's just not going to be stump puller or an RPM machine. It will give you good mid range and cruising ability on par with a 350.
