Hi Garry. I fitted a Getrag to my 280SL, and never regretted it, makes the car much nicer to drive. I would say, however, that I tend to agree with you that such upgrades, particularly non Mercedes, may prejudice some later buyer. For that reason I kept everything of the original four speed installation, and would urge others to do the same. I also bought another drive shaft to shorten, so the original could be put back, although, not while I own the car !!
Cheers, Dale