well the 305 is a 305 shares the same crank with the 350, but the bore is much smaller, just measure the diamaters of the blocks with a tape measure or ruler, if there the same you got 2 350 blocks, diffrent, the smaller 1 is a 305 or smaller. If the engine you got from the guy spun a bearing, your going to at least have the crank checked by a machinest, and all new rod bearings, if a bearing spun, it's no good.