I have done about 6 of these conversions, including my partners 71 w/auto trans. Even did one with a chevy V8 in it. It really worked good on that low reving motor.
The one we put in my partners car was a positraction unit and caused some special problems accomodating the breather hose. Its seems the limit to the number of these conversions that we do is the number of good 280SE 4.5 rear ends we can find.
Bosch Master, ASE Master, L1
33 years MB technician