I have a 722.4 from a W123 280 from around '85 or '86, and would like to use this box in my 300D from 1978.
There is I believe a 722.1 in it at the moment which seems to slip when cold. I say seem as I'm not familiar with diesels yet. From reading forums this could be due to the pump, but as I said I'm a newbie.
Cutting a long story short, if the 722.4 fits and it looks like it would this be a good swap.
thanks

What's your neutral safety switch look like? You'd also need the throttle linkages on the valvecover.

The switch, until I replaced the nylon bushes, worked fine. At the moment it only works in park, but that could be adjustment as one of the bushes was completely gone.

The 'new' gearbox comes from a parts car, so I should have everything. Or does the throttle linkage has to come from a diesel?

Well I was wondering if your 78 would plug in fine into the 722.4's NSS. I have my doubts about a nondiesel linkage working but I don't really know. You don't need all of it, just the bowden cable part, so you might have luck.