If the truck is as clean as it looks, then $3500 is not a bad price as todays price`s go.
If it is just the OC and that is the problem, not a big deal easy fix. Just time consuming and an oc seal kit.
(iam an expert after doing my 86 3 yrs ago
) how ever it`s just a pain in the rear flushing out he cooling system, doing quite a few flushes with Dawn and enough flushes of water to get it clean.
Goat