I have been watching a 2 ton wrecker...the owner put $2,500 into the brakes, it runs, and has no rust...problem is...No title. I could have bought it today for $1,500....the truck is in great shape. It spent life in a scrap yard...
Add up the cost of all of the good parts on the parts truck, use realistic pricing for what you see; rear fenders, floor, that rare front lower splash pan..then decide what you are planning to replace on your truck...if what you need to spend to replace your parts is high...keep working on the guy....otherwise, walk away.