I was looking at an 88 Iroc, and the guy says it has knock and claims that a new crankshaft will fix it. or a new engine (well no **** eh?). its a 350tpi. How much damage could I cause if I drive it home? (about 40 miles). How much are the odds that only a new crank will fix it? Or would a new lower end be in order?

Depends on how bad the knock is and if its even a con rod or somewhere in the valvetrain, if it hammering pretty bad i wouldnt try driving it but if its a light knock id go for it.

Depending on whats making the knock, If its con rod bearings shot then check clearances and get new bearings. If the bearings have spun and screwed up the crank and depending on how badly worn the cylinders are i would opt for a complete rebuild or even a new motor.

I guess I was bad and got deleted....my main point was buy this thing at your price and expecting do to major engine work...don't pay his price.