Oil pressure: You need an idiot light, it doesn't monitor oil pressure in the M unit, but you do run power to the light from Aux 1 or 2.
Speed sensor: Correct, This is just so the M unit can track your rides/service intervals. You split the signal wire from the sensor to the Gauges and to the input on the M unit.
Reg/Rec: As Brian says, you can't use the original reg rec units
(edit: with a lithium battery). You should also not use a cheap eaby unit. I bought the Ricks reg/rec, expensive, but they are tried and tested.
This is the best diagram I have found, It's also editable in illustrator.
https://technicalarticles.revivalcycles.com/hc/en-us/articles/360009106131-m-Unit-Blue-Basic-Universal-Wiring-Diagram side note: The M Button will not work unless installed inside steel bars, so if you are going aluminium clip-ons, don't buy one.