Dear Gordon
I would recommend to disconnect those cable feeds at the fuse box. Is not good to have positive leads energized and not connected even if you apply any kind of electrical isolation to the cable ends.
List:
1. Kick down switch, the positive lead is cable, RED/black stripe coming from fuse 3.
2. Positive feed to Iddle Swicth. Cable RED/black also coming from fuse 3. The return lead from Iddle switch is BROWN/white
3. Iddle Increase selenoid, cable BLACK/green/red coming from fuse no.5
Confirm each cable before disconnecting from fuse box by using a continuity test to the corresponding end at the accessory itself. Remember these cables are old and the Colour stripping is not always perfectly visible.
If you disconnect those 3 leads at the fuse box, by means of cutting the cables or removing the oring connector from the fuse box terminal screw you will be on the safe side. None of the other cables that service the automatic transmission will have any power. In any case there will be just ground signals on some of them.
Regarding the Parking/neutral reverse light terminal.
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You have to re route the cables responsible for the return /reverse light signal, which are the gray/yellow and black/yellow/red (feed 12v from fuse 5) to the new reverse light switch at the manual transmission gearbox.
The cables for the starter selenoid signal, violet/white (input) and violet (output) must be joined together or passed through as you mention a starter killer switch ( remember large enough to handle this load, about 12 A or more).
Best regards
Eng.Leonardo Peterssen