W201's used the 722.4. W124 260e's 300e 2.6 and some early 300d's used the 722.409

The 2.6 litre engine of either the W201 190e 2.6 or the W124 260e (300e 2.6) use the 722.409 transmission.

The 722.4 transmissions in the W124's and W201's used a different ratio diff than the 722.3 equipped cars.

The 722.3 transmissions handle a lot more torque than the 722.4 varieties.

I have installed a 722.3 transmission in a W124 260e. It wasn't very successful. The 2-3 gear ratios were sluggish in combination with the diff.

The main physical differences between the 722.4 and 722.3.
Torque converter splines are different
The connecting flange between the tailshaft and the transmission on the 722.4 is smaller than the 722.3
The kick-down cable connector on the transmission is physically a different shape.
The oil cooler lines that run off to the radiator are different lengths and different banjo bolt diameter at the transmission end.
The 722.3 is around 3 -4 inches longer than the 722.4
The 722.3 is 50% heavier than the 722.4
The transmission dipstick tube is a different shape - the 722.3 is physically bigger.

For ease of installation you need a 722.409 transmission for the W201 190e 2.6
A 722.4 transmission out of a 4 cylinder W201 190 is a risk.

To install the 722.3 in the 260e I needed to
(a) use the torque converter from the 722.4 in the 722.3
(b) Change the rear tailshaft/flexdisk connecting flange from the 722.4 to the 722.3
(c) cut the kick-down/lockout connector off the 722.4 transmission and splice the 722.3 onto the wiring to suit.
(d) Change the transmission to radiator oil cooling lines.
(e) Adjust the vacuum regulator to set the shift points correctly.
(f) Install the 722.3 dickstick tube

The 722.3 transmission fitted into the W124 260e however it maybe too large to fit on a W201 body.

When you have the transmission out, change the rear main engine seal.