A little info is needed?
Are you going to do this motor swap inside a shop/garage? Ceiling height?
If inside a shop, I would think taking the back cap off, and taking the motor out the back would be the way to go!
If doing this outside, then jacking it up far enough to get the motor out from underneath, leaving the back cap on and weather tight!
Not the job for the meek, that's for sure, but doable, and there are plenty of old 8.3's laying around!
On my 96 Windsor, and a buddy's 93 Dynasty, the access from under the bed is really open and good, so getting to the top of the motor will be good!
Removing the rear cap, other than it being awkward, would not be too hard with some help from a few friends! You also could do some insulating and sealing it up better than the factory did, while you have it off!
Good luck, and take a bunch of pic's and start a post, so we can all learn from your experience! Rail!
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Retired, and "Always on Holiday!"
1996 Monaco Windsor 38PB, "Mona" 275 HP., 8.3 Cummins, 3060 Allison 6 speed, 2001 PT Cruiser, "Bailey"