The 124 chassis and the 190 both came with five speeds optional. they were extremely rare in the 124 and more common in the 190 so there are some out there in the salvage yards. you should not have to change the diff or speedo, but you will need the tranny, shifter, pedal cluster and driveshaft. possibly the cross member too.

afik that should be a bolt in.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.