The 722.5 is like 4" longer than the 722.6. The 722.3 is nearly a direct swap. Just redrill the cross member and shift linkage for the .6 later. And you do not need a custom driveshaft or import parts from Europe.
And yes. The factory computers all need to get info from other computers. Even ABS wheel speed is required. Just a simple run engine early 90s stuff is at least HFM, EA,CC, ISC module and wiring those up and get them to work with current ABS system.
IF you want an Me computer with 722.6. Then you need the factory Traction computer and tcu from the same donor or like. And speed sensors set up etc. etc. etc. Then correct gear ratios. Tone rings for said sensors. And a bit more I imagine.