Ya I am not sure what full floating rear you would be talking about that would have a removable third.

My 609 does, but that is beside the point.

If you are truly talking about a removable third then you have to pull the shafts, drop the d-shaft, remove the third, and RTV in the new third, bolt it back up, replace the d-shaft and axle shafts.

Not that big of a deal. Prob. take an hour in all with lube change and gasket material.