I would not tear it down until I had a line on parts. The engines were very tough, but never found much favor with truck buyers. Since they were so tough, dealers didn't stock many parts for them. For this reason, not near as many parts for the V6 appear on eBay as other engines. There are usually some valves on eBay, but pistons are a rarity. Try soaking the engine for a week or so with something like Marvel Mystery Oil. I have seen a lot of engines free up and then run a long time. What do you mean by numbers matching? Unless you have the original line set, there is not going to be any documentation of the engine serial number. If you do have the line set, the vehicle is still not going to be worth a lot because of lack of demand.
