Brian - what you should have is this:
From the igniter unit, there are 2 sets of leads coming out. One plug is for the 4 wires coming up from the 2 igniter coils (pick-up coils) on the end of the crank. These should be blue/black and yellow/red. I am pretty sure the blue/black wires are from the l/h igniter coil and fire 1&4, the yellow/red wires are from the r/h side pickup, and fire the #2&3 coils.
The other lead from the igniter unit goes up to the ignition coils - well, 3 of the 4 wires do but you can't see this once you plug into the main harness

. The colours coming out of the unit are green, red/yellow, black and black/yellow. The black/yellow is an earth for the igniter unit and does not end up anywhere near the ignition coils. The black lead goes to the #1/4 coil, the green lead goes to the #2/3 coil. The red/yellow lead is the +12v feed to both coils - where the small lead from the igniter unit plugs into the main harness, this lead changes colour to plain red.
Hope that helps - the GT motor is just the same as far as the basics go.
One good mod to do to these old battery/coil systems, is wiring in a normal 12v Bosch or Hella relay into the power supply for the coils. This ensures a good solid +12v power to the coils, instead of the power coming through the wiring harness to the ignition switch then through the kill switch and back into the wiring harness before being plugged into the coils.
This is what the wiring diagram looks like - its dead easy to knock this up and it makes a big difference to starting and general running.
