Well okay, I've been following this thread now for a few days and just thought I'd throw in my two cents.
While I do appreciate ambition and respect forward thinking individuals, I must say there is something to be said for moderation too.
Since this is your first project and based on your last question of where to start I would highly recomend that you re-think some of your choices.
First of all, although it would be "cool" to have a diesel powered, granny geared big wheeled monster truck, just how reasonable is actually accomplishing the task of fabrication? It sounds like you have access to all the hardware and facilities but when you start talking about 500 dollar adapters for the transmission (that's just one small part of the build) and trying to cobble in a 6bt and MAJOR bodywork intrusions into the cab....well I think you get the point.
You may be just as happy with something a little easier to accomplish (build) and get out wheeling without spending your first two years of college tuition. Afterall, the desired end result is to have a drivable, somewhat reliable, piece of rolling stock that you can go out and have fun with. Not have a "project" that may take years to build, get right, invent and reinvent every little aspect which will undoubtedly lead to boredom and possibly abandonment of the project altogether.
I really don't mean to sound like a downer nor rain on anybodys parade but, what about just dropping in a chevy 350, a crawly 4 speed and some tires and just run it for awhile? It would be much easier and wayyyy less spendy than some of these alternatives suggested on this thread.
Again, never to put a damper on anyones dreams but maybe just a modicum of planning and execution would yield a much higher end result.
Just my two cent's.....and absolutely best of luck with your plans and accomplishments.