Been following this with much envy.
Yeah, I'd love a 6BT. No, I don't think I'll ever afford it
If you take your time and wait for the right parts/vehicles to come along you could do it pretty cheap.
Example - A rust free (Texas truck) Fj60 I should have bought - $1600
A 1993 Dodge w/ Cummins - $1800
Add in SOA kit, intercooler, re-gear, new exhaust, metal for fabbing, material, brake lines, etc and you add another $1500 on the very low side.
Get an old beat up W250 farm truck and run the dana's under the cruiser, along with the trans and tcase. Easy in the sense you don't need an adapter, gearing's the same, brakes are able to handle it. A little less to worry about at that point.
That's for a bottom end swap, of course you can go as extreme as you want. If you have a place to keep it take your time with it and save as you go. I started in July of 2012, being a fulltime student, on a small budget. I could hae certainly done this project for a LOT less money than I am.
I'm hooked on builds now. I'm set on doing a Fj60/62 VW tdi swap (1.9 alh with at least a stage III kit, which puts the power at 150hp and 270tq) one day before too long. Tried and true motor as long as the timing belt is done regularly, no need for an SOA, the only problem I see is getting an adapter for the transmission.