I've been looking into that combo for a swap into my 74. I believe, but I'm not certain that, you can take the ax-15 geartrain, and use the r-154 mainshaft and tailhousing and blend the two. I know ax-5 and g-52 stuff can swap, not positive on the big brothers. So I think that would solve the flywheel clutch problems.
Edit:
Sounds like with the 94-99 bell housing, custom friction plate(Otts Friction supply?) and an extended pilot bushing(advanced adapters). Then you'd have the benefit of the 11 inch clutch