Building a GTO, needs some advice
A nice HCI would do wonders for the road course too, you don't want all that weight of the turbos and intercooler over the front of the car...it's already a nose heavy car.
I went with some good stable/light valvetrain and a forged bottom end, along with the IR scraper and pan baffle for better oil control.
You have a tough road ahead of you. I dumped my 04 GTO for my 95 camaro since the aftermarket is so slim for GTO's. Looks like you have a decent setup on it already suspension wise.
Make sure the radius roads are up to snuff with all that autocross braking. I just fell in love with HP+ pads over HPS pads this past weekend.
Dump the 19" wheels and go 18" for better tire selection. Unless you got CCW/Forgeline etc and get custom wheels I think you will find it hard to get some decently wide wheels that fit the GTO wheel wells....the front specifically. I also think the GTO is camber challenged due to suspension. C/O may allow you to run more than usual. Miker (I think is his name on ls1gto.com) got his car setup for autocross and he was able to stuff 285's all around with the right combination of parts/settings...Stock Fbody's can fit 315's fairly easily (just a comparison).
Lastly...it's a heavy pig to toss around corners LOL. But it will be a damn BLAST if you have never raced!
Goodluck!



