I think you need to list your needs/likes and do pros n cons for each.
Do you need a live front axle - this will lift the fifth wheel.
Do you want a full on military look or a militarised civi truck - M915... either CCC or Freightliner will be cheaper for parts.
Likely that cruising speed will be compromised with 6x6.
Are you ok with modified Military look - ie., neutered Deuce/5ton.
Are you going to only military shows, do you want to drop n display the tractor on its own.....
... there are a myriad of options but until we know where your heart is you are going to get a lot of suggestions - perhaps that is what you want if you really have no preferences...
One idea - get a used civi FLD120 (M915A2/916A1 look alike) real cheap!, and militarise it with a grille guard, green paint, antennas etc., 70+ cruising speed, lovely interior, creature comforts etc.