You need to get some cooling to those brakes man!
I'm sure you've seen this build:
http://www.vorshlag.com/forums/showthread.php?t=7806 lot's of good tech in there if you haven't checked it out already.
Oh yeah. I'm not planning on tracking this car for the very long term, so no cage, no BBK, etc. I'm doing 3 inch cooling ducts from the front fascia. Front bumper's actually already off the car. Got new dust shields ordered for the brakes with the proper connections. Going to DIY the rest out of ABS and/or fiberglass.
From the other mustang guys I've talked to, the 4piston Brembos I currently have with good cooling, pads, lines, and rotors will be fine. If I do a brake upgrade it'd be to a real race caliper that supports 24mm thick pads. And that's $$$$$$$$$$$$$$$$$$.
Stop tech has some good shit. They?ve got a warehouse on the south side of Chicago so, parts availability is easy enough.
I'm shopping several different vendors for 2pc rotors, but I'm seriously questioning the cost. It approaches 1k. That'll buy me 2 events including consumables. Every upgrade I make right now has to pass this test:
"Is this more valuable than the amount of track time the $ would buy me?"
The 18s + tires are a long term cost savings and cheaper than a new set of 19s... so yea.
The 4 point Scroth Quickfit Pro are a safety item and will allow me to wear a HANS in my stock seats. I consider safety items numero uno so cost there is irrelevant (Plus they're only like $350, and I'm borrowing a buddy's HANS while he doesn't have a racecar).
Brake cooling ducts should make a significant difference for only total cost of around $200, so definitely worth it there.
2pc rotors? At $1k? Ehhhhhh. I can get really nice EBC dimpled and slotted rotors for around $300. I'm waffling hard here.
I'm genuinely a pretty bad driver so the more ass-on-track time I can get the better. I'm not out to build the mustang into a full on racecar. Long term plans a tow vehicle and real racecar. A buddy has an extra Pro-Challenge chassis in his garage that I've been eyeing.