A:
My buddy has a machine shop so the mods were easy enough. The easiest way to determine what you will need is to compare the transmission you're replacing (you mentioned a three speed)to the T5.
Put them side by side and measure them up. You may get lucky and only have to repalce the clutch and PP. We were replacing the old 4 speed rock crusher trans, and had to cut the input shaft drill our the mounting holes and trim the bearing support. In any case even if you've got to perform the same work we had to and don't feel comfortable doing it yourself and good auto machine shop should be able to do the work reasonably.
JimBo


Bubba