Your best bet is to find someone selling a PS box, bracket, pump, lines, etc...pretty much everything you need. Used these go for about $450-500; depending on the PS pump, etc. Shipping can add a bit. Most of the time, the gear boxes are fine....you can send them to West Texas Off-Road and have them rebuilt for ~$170 (~$110 or so for the rebuild and $25-30 shipping each way). Factor in a collapsable steering shaft, new ($225) or used (~$40 + new ujoints and rag joint another 30-40) and possibly a rebuilt PS pump ($50-150) and you are close to the price of the expensive kits. People can and do find deals...but steering setups are more rare...so they have a fairly stable market value. Be patient on the gear box or snatch up a complete set-up...otherwise fork out the cash. My advice is whatever you end up with upgrade the pump, get new hoses and go ahead and put a strengthening plate on the frame if you plan to wheel the truck. B/C of all the variances between different vehicles, engine swaps, belt arrangements under the hood, etc...its hard to say whats "best" or universal...but there is alot of info, if you read through the posts and look around. Good luck.
John