Installing a 722.409 from a 190E 2.6 into a 300E 2.6, what to replace?
 

I have a 722.409 from a 190E 2.6 that I am selling to a guy who will have it installed in his 300E 2.6 which also has the 722.409. What should he replace?

I know he should replace the filter and pan gasket, dip stick tube o-ring, transmission mount, vacuum lines going to it, and the transmission cooler lines, but anything else?

...I can only pedantically add fresh ATF! I think you've got a good plan.

You might want to look at the flex disc, engine mounts and the shifter bushings but really we could then carry on and do the rest of the car...

...don't forget to do the rolling the car on four wheels trick before tightening everything down to avoid driveline vibrations.