1. That number is based on putting in a Herc diesel (new) with all adaptors,
rewiring, changes in fuel sytem, exhaust, instruments etc. and complying with
smog requirements in California. Plus, regear both axles with rebuilt diffs,
new hubs in front, dealing with 24v to 12v electrical adjustments and a number
of other small changes. This is the high ticket package and will end up
costing $10k before your own cosmetic changes. Better add power brakes while
you are at it. And for a daily driver you should use a good set of radials,
not the mil ND tread. If tall enough, they will offset the need for axle
ratio changes.
2. With stock Chevy or other popular repowers it can be done for less. Using
rebuilt or just take out engine and other parts your cost goes down.
3. If you are good with making your own adapters, improvising with a welding
torch, swapping gears, wiring changes, etc etc etc you can bring the cost down
further but at the cost of your time and effort.
Bottom line: you could swap in a Chevy with some homebuilt adapters made from
other vehicles and minimal new parts in the low thousands. Better yet, as
others have suggested, buy someone's project who is tired of it and is not
trying to recover what he put into it.
chuck