I would suggest you to stick with the stock configuration.
I have a diesel 80 and it was originally full time 4x4, the last owner installed manual hubs for the same reason.
I did use the manual hubs for some time as RWD car, on top of that i was using the Mud tyres.
The mud tyres had poor traction and a couple of times my car skid while turning fast on main roads.
As part of the restoration I went back to original full time 4x4 configuration and never felt the traction problem again.
Personally I didn't feel any change in the fuel consumption either.
I think its more safe to drive as full time 4x4... just my opinion.
Cheers