Typically it has been assumed the automatic trans and the 4 speed are the same length on the W123. So like on my swap of the 617 into a 240D car, we just take four inches out of that short front section. The engine is 4" longer, the trans is backed up by 4" because of that additional length and we shorten the drive shaft by 4" and everything works out. Now you are using the original type engine and if the transmissions are the same length, then the front drive shaft "should" be the same. It is hard to measure the overall length of transmisions unless the are out and you can put them up against a wall. But I would think that your original front shaft would be right.

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Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!