Buy it provided everything else is well maintained and no rust.

There are several shops in NW US, OR and WA in particular, that will do a 3.4 swap for ~$3k to $4k -- labor, engine, and special parts.

I believe the tranny you want is the a340f, not the a340h. But any 3.4 swap shop will be able to walk you through the specifics. The a340 tranny series is very common. Jeeps and a few others sport them too.

At the $400 price, you can have a new to you engine and tranny in for a total investment of less than $5k and do no labor. If you want the engine and/or tranny rebuilt you're going be in the $6-7k range, still doing no labor. A very good deal even w/o DIYing IMO -- the more I think about it, the route I'd go if I were to buy mine over again (talking the wife into buying and rebuilding a truck w/ a blown engine would be another matter however).

 

Valve adjustment plus standard reliability maintenance while you're in the neighborhood like coolant lines and vacuum lines near failure will add up to ~$1000 if you pay someone else to do it all. Add in timing belt, water pump, etc, at least one or two failed sensors, failed oil gaskets/seals, and you're at ~$2k. You can save some $ diy-ing, but not a lot relative to other jobs. OEM parts are expensive.

Bang for buck is on the busted rig for $400 w/ immediate swap.