Hey John
Yep that 9" I sent over for you is fine for your coupe. It's out of a XC GXL, I think it's a 3.25, I can't remember off hand now, I've got so many here I forget which is which. But I know that came out of an XC as I pulled it out on my own the day before the container was packed. It will bolt in fine.
YES you will need a proportioning valve as it's a disc brake 9". You can either get a GT one from over here, can help you there. OR there is after market valves available there. I think I can find out where to get them and send you there.
No probs with the different brand brakes. The brakes on the rear were always the same, they varied in some ways, e.g drums, front or rear mount calipers. But none of that is effected by the brand of the front brakes.
The only difference in the 2 different brand front brakes realy is the Girlock have a MUCH larger surface area on on the pads.
Yes I like Tim Tams.

You can still ask about another 987,435 questions before I scream.

The Interchange list is being constantly updated as guys like yourself find new parts that will match up to the Aussie Falcons, so any you find please let me know so I can share it with all.

Not sure on the fan shroud. I'm guessing no, as I've sent about 3 shrouds over in the last couple of months so I guess those guys would have tried some US ones first, but I honestly would be suprised if there wasn't a US radiator that was the same size and shape. I'll let you know if I find one though.
Wiring Harness a pretty well priced actually, well worth buying them over tryng to make your own. Email me and I'll give you the options.
See ya
Cam