D30s don't have lockouts right? Which means that your front would always be locked if you put a locker up front. That would only make your locker issue worse on trips. I would definitely put it in the rear before I put it in the front with no lockouts. As long as you don't get a crappy locker you will be fine on the highway with a locker in the rear.
Yea I guess you would be right. It is disengaged at the transfer case. The whole front axle has no power to it but is spining while moving.
1988 Comanche auto, 4.0, 4x4, 8.8 rear trussed, Dana 30 trussed, SYE np231, Serious Offroad long arms, 9.5" of lift, 35's, lockers