The differential on my 87 300 SDL has been on its way out for a long time now. I was looking for a suitable replacement in the local junkyard. To my dismay, I found no 300SDL's, but I did find quite a few second-gen w126 chassis long wheelbase cars. Specifically, I found a few 420 SEL's, a 500 SEL and a 560 SEL. I understand some, if not all of them have different gear ratios than my car's. My question is would a differential from one of these cars will be a drop in replacement for my car and which one would have the most beneficial gear ratio?

__________________
1987 300SDL