Aside form the aforementioned tangs for the front of the paralever strut, the only differences between transmissions are:
a) 1990 and later (including mono and parlever) the metal of the trans input splines is supposedly harder than the earlier splines.
b) When putting a para trans on a K75 the fifth gear ratio goes from 1.67 to a slightly taller 1.61.(same for all 4 cyl bikes) About a 3% difference - probably something most people wouldn't notice.
Aside from that it's bolt on and go.....