Personal experience, I've had a twin-locked Patrol and I would not do it again unless it was a comp truck. The Patrol rear LSD is the best 4WD diff on the planet. Just leave it there. Put an ARB front locker in and call it good.
Before you get the center installed it'll be worth giving the LSD a freshen up, they can be shimmed up to work very effectively.
After 35 odd years and a few hard yards it probably won't be as tight as new.