I think that you can buy a basic rebuild kit for something like 800 bucks. The real cost in a quality build is the machining. Get the thing blueprinted and straightened out b4 you build her. Make sure that the people doing it will bore ALL THE CYLINDERS THE SAME. This is one of the major differences between a quality build and a mediocre to crappy one. The machinist should go and bore out the cylinder that needs the most to straighten it out, then bore the rest to that diameter. Don't go cheap and just have ittorn down and new seals, gaskets, and rings put in. get it machined right. The cost of this will depend on the shops that you go to, so check the local machinists, and see what they want, and will do for it. Sorry if this dosen't help you too much, but it really depends on the machinist.
To put it mildly, cost is proportional to your ability and willingness to do the work.
It also depends on what work is needed and what you plan, as well as what needs, to be replaced.
As an example Rock Auto has a rebuild kit (mostly Sealed Power parts) for $600 that includes:
stock cam(with lifters)
timing gears (metal?)
full gasket set
Brass expansion plugs (freeze plugs)
This is just a starting list. It wouldn't be hard to push the parts to well over $1200. You'll note that this doesn't include any head or block machining.
If you have a shop do all the work expect the bill to start around $2000 for a basic job and climb from there. If your willing and able to do the lions share of the work and just have the machine work done then you could cut the costs way down. It's all dependent on your skills and willingness.
Do you know what it typically costs to rebuild an Inline 6 engine?
The absolutely FIRST thing you need to do is get the Block Manaflux'd to make sure it's not cracked is some manner, after that a Standard rebuild by a Competent builder is $1,500.00 - $1,800.00.
To B&B & P&P build starts @ around $2,500.00, though you can just have the shop do all the Machining required & do the rest of the build yourself.
When I did mine twelve years ago I had the machining work done by a build shop, then assembled and installed everything myself. 1000-1100 dollars. And I mean really rebuilt. Head milled, bored, crank turned, main bearings, pistons, etc. etc.
You might figure prices have gone up a bit since then.
The only problem here is I am no mechanic by a long stretch.
I will need to have the entire rebuild done by someone.
So by the looks of this, its going to be pretty spendy. Cheaper than buying a new car though. And I love my truck. They sure as hell do not make them like they used to....