ok a little info I can add, as it seemed to launch pretty well out off the hole. Was a rx4 I had together once that on luke warm 245x17inx40ish slicks would get moving quite well. You could let the clutch out at 5500rpm and would just get out of there.
No idea what leafs are under it but they were different maybe lovells ? but as the set-up was quite stiff.(extra leafs) It had an added panhard rod bar and another bar that mounted from the top of the diff housing to inside the cabin and located to bracketry were the back seat should have been.
what looks to be the case before this modification. is that it was added as the diff flange/tailshaft yoke were wearing through the floor.this mod seemed cheap and effective but seemed to work well not sure you could talk you way out of it in a street car but