I do not know the answers to most of your questions to be honest. I would guess that you are probably going to have to see what swaps over and not.
For the things I might be able to answer. I would say that you cannot use your intake and that is ok you can swap over the throttle linkage and make the 560 stuff work. You can also just swap over to a cable drive pedal assembly with fair ease.
You could use your 4.5 fuel distributor and injectors and stuff. I think you might have to tweek the lines a bit.
Transmission driveshaft will have to be altered. The 722.3 is definitely a different length.
Mechanical speedo is easy. Just remove the tailshaft housing and swap in a drive gear setup from a car with a mechanical speedo. 300e stuff will just drop right in.
I do not know for sure about the speed being correct though. My guess is it will be fairly close.
No electronics on trans is required. But there is WOT detent for downshift.