I have run the Whipple 4.0L at LeMans, and Silverstone for 4 track days.... LeMans was 30C (98F ish), and Silverstone was 25C and had no issues.
Prior to that we swapped the 2 fans for race spec one, probably the ones Matech uses but I need to get back to you on those since I can't find the details in my records and David Jones (Mountune suggested the fix) is away right now.
On top of this they sealed the front air intake completely. If you take the nose off you will be able to see there are several ways the air could escape without going through the radiators....
The fans are VERY noisy (you can hear them over the Accufab at idle with windows up) and they do move a huge quantity of air (which can be annoying if you are planning on doing the occasional track day).
David is back next week and I will either get the details from him or will have him chip in directly.
Having said all this, if I was to build a race car off the FGT I would buy the Roush-Yates 5.0 Cammer engine and be done with it....
http://www.roushyatesparts.com/parts-p/m-6007-mrgt.htm