I've had a valve job done on one with more miles than that, and it ran like a champ afterwards (for a customer, not mine). No oil consumption problems or anything. With that being said though, for about the same price you can find a good lower mileage engine that you can just swap out. It's alot of work, but not as bad as it seems once you get going on it. Alot of salvage companies also offer warrenties with their stuff, so it's worth checking into.