As derrecuda has already said you wont need the MC engine management, but do try and get the coil if you can. The distributor will be the vac advance unit that your CGT should have in there already. I ran this setup for a while with good results.
Yes, your coupe GT uses a 5-window distributor which will generate the necessary signals to trigger the Stage IIb computer. Leave your ECU harness intact (you can strip out anything related to the flow plate wiring if you want) and tap the distributor wires for the 034 computer.
Forget what I just said, I forgot that the stage IIb does fuel AND distributor based ignition :slap:
You don't need any of the CGT ECU wiring, you're better off "rolling your own" as you don't need very many sensor inputs/outputs (TPS, Intake Temp, Coolant, distributor, coil, injectors).
You COULD use the CGT coil and distributor wiring but you'd have a lot of extra wire hanging around that would be doing absolutely nothing since the rest of the ignition harness is bundled in with it (not to mention the fun of slicing open the harness to get at the wires you would need to tap anyway).