isn't a 3A an upgraded TRS lower unit? i have seen TRS uppers advertized as Speedmaster-TRS. i see other people considering taking the bravo's out, moving the motors forward, putting the borgs in and upgrading to speedy's.

SSMIII/IIIA drives and transom assemblies are completely different from a TRS.

The SSMII was a TRS with a dual shaft Speedmaster lower unit. SSMII is 1" longer from input shaft to propshaft than a TRS. SSMII lower gear case parts are extinct.

What Biggus said is correct. The TRS and SSM III, IIA, IV, V, share nothing with the TRS drives. The SSM II was a TRS upper with a SSM II lower. That setup was weaker than a standard TRS. The SSM II lower was its own breed.