if a trade is an option, location matters. those things are a real bear to ship.
as to modifying it, the rear bars mount in the same place on the upright, and the same place on the fender. the angle/length changes.
do the vacuum balls really need to be XJ/MJ factory units? there should be others out there in junkyard land that would fit the bill. any chance that grand cherokees have something similar?
looks like you got a good amount of progress done.
the thermostat's job is to warm everything up. it doesn't help cooling at all. cycling the coolant sooner just keeps it in warm-up mode longer and burn more fuel as it tries desperately to get up to operating temperature.
legit snow tires are like having a super power. I had my minivan in 6" of fresh snow and it handled it great. I'll take snow tires + FWD over 4wd for snowy roads any day. and you can run them year round. they make fantastic rain tires too. cheap enough to just get another fresh set the next winter if you drive a lot.