Price on a used but good running 4-53T (from a very late 70's GMC truck probably the best place to start) seems to be around $2,000. I would imagine anyone selling one would include the 5 speed Spicer in the same price, because they are not worth much and most all are not OD. You will need OD to make it a useful truck with a diesel. My local junk yard just got one of these trucks in with a good engine, and for sale, PM me for the contact info.
OD trans options are out there, anything with a SAE#2 bell-housing, but expect to pay up to or about $1000 for a good used modern 6 or 7 speed OD, more for a small Roadranger 10 speed OD.
A used Spicer 3053A from a deuce and a half has a 0.80 OD (or is it 0.84?) they can be had from around $50 to $250 good used or government rebuilt.
If you do the axle and steering swap, Detroit 4-53T, and OD transmission, I can't begin to to guess at what it all cost for you to do right.. Although I have found excellent deals and prices on all the parts and components I need for my project, at the expense of time to research, wait for the right deal, and find the best prices, I still have a frightening amount of money in my project, and there is lots more to do.
I initially questioned you about your engine choice and suggested the 4-53, not so much because I think it is the best swap, but just to get you thinking and to explain yourself. A 4-53T, while I really like it, is not an easy swap into an AD truck. Even cutting corners, doing a half asked job, and finding everything in the junkyard, it will take lots of time, some money, and determination.
I much prefer the do it all right the first time method, even with the up front cost.
It has been said that "If you can't afford to do it right the first time, then you can't afford to do it over"
Grigg
