Hi Mike,
I have a '75 280C which is the appearance twin to your car, but with the 110 engine. My plans are to install a GM TBI setup on the car, but I will use the GM TBI unit from an astrovan 4.3 engine, and all the stock pieces - I think the inline six can handle the larger TBI unit. When I first got my car it had the vacuum assist pump mounted at the front of the engine, and whenever I went down a long hill the pump would catch engine oil, and the oil would then go through a hole in the diaghram and produce lots of blue smoke when I got to the bottom of the hill and stepped on the gas. I'm talking CLOUDS of smoke! I eliminated the problem by removing the vacuum assist pump and sealing the hole with a plate. The engine produces plenty of vacuum to run the brakes, locks, etc. on it's own without the need of the pump.
Congrats on a successful conversion!

__________________
Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C