i dont know if my wiring diagrams will help from an 86 model.
it is chassis specific ford/gm but not body specific from thomas/ bluebird.
my diagram shows a terminal strip and says on the fire wall left of the driver.
with 2 N2 terminals towards the right end of the strip for start interupt positive and the second for ground.
i have posted these here before but cant remember where?
maybe in my profile but probably in an old related post.
motors shouldnt really change the factory wiring except my diesel doesnt have glow plugs or pan heater,block heater stuff.