The bell housing bolt pattern is unique to the M120, however, if I have it right, the crankshaft bolt pattern is the same as all the V8s which went before the M120; M116,117,119. Eight bolts, seven at a radius of 40mm,one at 38mm. Hence, any flywheel that bolts to the earlier engines will bolt to the M120. I have modified a Ford 4.6 8-bolt flywheel to fit the pattern in question, which allows use of clutches up to 11 inches if there is room in the bell housing. The starter ring gear diameter may also be the limiting dimension.

The bell housing will be custom, which opens the door to many transmissions; Tremec T-56, 6060, etc., etc.