There were some 3rd members that came from the factory with 4.87 gears during those years that has no aftermarket support. (no lockers, no gearsets, etc) It has something to do with the design or something.
That is not totally true, there is away to use any of the lockers in that housing. I do not know the details but I read about it on PBB a couple of years ago. It is something like using the 4 cylinder full locker (ARB, Detroit) with V-6 bearings. By the way it is 4:88 not 4:87.
Yes you can cut all the coil stuff off the runner housing and add leaf spring perches. A lot of people do that when the SAS the front on the runners.