First off, hold all the "sink the ship" crap. I'd like to hear some constructive criticism of the car and how you'd improve it.
My thoughts...
That rear spoiler is just lame. They should've left the Monaro's rear spoiler on it. It's much lower/form fitting and doesn't look so "add-on"ish.
The same w/ the wheels. I really liked the 5 spoke (almost Rally II) wheels that the Monaro has.
I would really like to see an 65-67 hood scoop, although it needs to be much larger (If any of you are familiar w/ the 1968 Cougar XR-7 G model, you'll know what I'm talking about). I think that would fill the hood nicely. Although the Judge-ish avatar that 2004_GTO has is kinda nice w/ it's 69 styling.
The biggest styling cue I can think of that would really help the front end is to set the grilles into the fascia about 2 inches. It would give it more of a personality.
I'd also lower it about 1 1/2 inches and swap on some meatier rubber.
I think that'd give it some old looks and some more attitude.
John