Hello'
Please read my previous post, the W114 is ALL six cylinder 2 and 4 door bodies, the W115 is ALL four cylinder and the sole 5 cylinder diesel (240D 3.0 or 300D in NA). ALL share the 108.3 inch wheelbase, the coupes have a lower roofline with a smaller rear screen and are pillarless (hardtops for Americans!)
There were no zero ofset front suspensions before the W116 of 1972 and W123 of 1976, all prior designs have positive offset steering geometry.
The W201, W124 and R129 and ALL models after these cars, eg W140, W210 etc. have NEGATIVE offset front steering geometry.
W108 were a restyled W111/112 (fintail) with bigger 2.5 and later 2.8, 3.0, 3.5 and finally 4.5 (USA only) engines, all the details of the running gear are similar to fintails.
W114/115 were a somewhat radical departure for DB and the basic rear suspension was used in the R107, W116, W123 and W126.
AFAIK, the only interchangeble part is the suspension arm itself, and perhaps the differential assembly.
The front suspension from the W114/115 was used in the R107 only.