I think a bit of a recap might be in order, lets remind us all on what the original issue was, and what has been suggested and checked so far; otherwise we are just going round in circles;
The original issue of the partial seizing was found to be the clutch case bolts touching the two small bumps in the bottom of the gearbox casing, I am not sure any of us was aware of the ring gear also scuffing the case at that point, so our main concerns were first; are the correct bolts and washers fitted to the clutch case, next, is it the correct clutch case, next is the flywheel fitted correctly, i.e.; was there an even space between the flywheel and engine case at various crank positions, next, has the engine case been machined [not likely] next is there a possibility that the crank has been fitted to the engine correctly [unknown at this point]
There has to be a reason why the crank, flywheel, and clutch case all seem to be too far back, or protruding to far into the gearbox casing when both the engine case and gearbox casing are bolted firmly together, it may only be a few millimetres, but its enough for the clutch case bolts to foul on the gearbox case bottom.
Hope this helps.
Ant.