I did a Wilwood big brake upgrade on the fronts last October. I upgraded from the standard SL4 caliper to an SL6. I have 15" wheels and all I needed was a 3mm spacer which I ordered from Skulte Performance. They customed machined it to my specs and all is GREAT! No fade on the track now.
The rear calipers on the early cars require a simple bracket to be fab'ed to go from a cast iron 97mm spaced Ford floating caliper to a narrow mount 5.25" Wilwood dyna pro. The offset needs to be .835" . I did mine this last summer with a .810" x 11.75" GT directional vane rotor with a .720 depth aluminum hat. USe a 45degree adaptor from the brake line to the caliper for wider wheels
You will not need a spacer for this.
Rumor has it though, there is something in the pipeline on a Brembo big brake kit. It is only a rumor at this point, and has only come up in drunken conversation, from somebody who knows somebody....etc. You can do a Wilwood upgrade all the way around for about $3000. Double it if you want a Brembo name.
If I continue to track this car, and carbon/carbon ceramic brakes come down in price, I wouldn't mind putting together a brake system for my car from Brembo.
R