I'm not saying that at all. I'm just showing that apparently there are aluminum radiators floating around in the universe besides Mishimoto's. If anything, I think there's several customs radiators out there that were made on a case by case basis and not for public consumption.
Just an FYI, someone reached out to CSF Radiator about a year ago and apparently they were working on one, no updates since. You may want to inquire....
http://www.fiestast.org/forum/cobb-tuning/5329-radiator.html
As for STOA FiST having an aftermarket radiator or not, it's all up in the air unless someone can show a photo either way. Personally, I don't think the car needs it for the type of use the cars were getting at STOA.