No worries DJF
from what I have seen

short plunger is for all 56 4 speed and STD pattern 60 5 speed gearbox reverse switches

long plunger is for dogleg 60 5 speed rev switch and
top gear (4th) indicating switch on 60 4 speeds

I have pulled an extension housing off a 5 speed and it looks like a fairly simple task to drill and tap from the rear thus getting around the old "60 5 speed into a 1000/1200 problem". Leveys approach sounds easier!