85 Sierra Need Some Help!!

Well i purchased an 85 sierra and come to find out the crankshaft is in need of replacement. So i bought a crankshaft and all the gaskets im going to need. I was talking to another mechanic the other day and he said well what if the engine is damaged? And i really didnt have much to say about it cause i dont know what the hell im gonna do then. If the crankshaft doesnt end up working out is there somewhere other than a junkyard where i can get a carb. 4.3 v6?