Originally posted by MTI
You will need to change the radiator shroud, engine cross support, ECU (engine computer), transmission
Not true - the 2.6 transmission is the same
722.4 is used in in 190E 2.3, 2.3-16, and 2.6, with 6 Bolt small Pan. Also used in 300E 2.8 (M104 engine), so you could go to 2.8 without changing tranny.
722.3 in all 300E's with 3.0 inc. 4-matic, with 6 Bolt Large Pan
You'll need larger radiator, but how you do that is up to you. You could install the 300E radiator, possibly with no mods to the slam panel and frontal area. The 190E 2.6 factory though has a different slam panel and front. If you wanted to exactly copy that, you'd probably need to change the metal at the front. I think engine mount positions are the same.