Yes, that is the ONLY one I know of (the T-2R), and the pre-load is the major difference in bias ratio between it, and their more pedestrian/factory installed as stock, T-2 diffs (~2:1 bias for the T-2, ~4:1 for the T-2R, at least as they were used in 4th gen, 10 bolt rear axle f bodies).
I agree with you on the above, and was only asking if
YOU knew of a way to change the 'on the shelf' bias ratio of any of the available Torsen/worm gear type diffs for our cars (when you sort of implied that by saying "the correct bias ratio", as if they can be changed) , since I thought it was impossible to change that from how they come from the various manufacturers.