Re: 1987 force trigger wiring
You do have the system that makes connections at the terminal board on the bybass side of the engine don't you? Not the Prestolite that uses made up harness with quick connectors?
It's been a long time since I mucked about with this system, but I think the factory original had a signal and ground wire paired for each cylinder's trigger. It sounds like the replacement has a common ground for all three triggers.
Hope you made a sketch of the wiring or took a photo before you removed it so you know which color goes where.
So hook up the three trigger wires to their respective terminals, skip the ground terminals, and hook up the single ground to the common ground terminal. Should fire up.