It's been a while but as I recall you can disassemble the frame members around the "C" drive upper and then easily slip in the new mounts. The "C" drive is happy to sit by itself on its "trumpet" and the big rubber hose while you do this. Then adjust the mounts to "share the load" with the trumpet and retain alignment with the transmission output shaft. You could loosen the clamps on the hose to be sure it seats happily, but will likely be back in exactly the same orientation. Can certainly be done in the water.
SN68 Sangaris, Tropic Isle Harbor, FL