I had a custom dual pass rad made by Fluidyne to my specs for $340. Fat 2" core, dual pass, mounting plates for stock holes, correct size inlets and outlets(no adaptors or weird sized hoses) and with a dual pass unit both hoses come out on the same side so there is no long hose to cross infront of the engine. Never have a cooling problem, even on the hottest day.
There racing division makes up custom units all the time, speak to Keith Robertson. He is in charge of there racing program. They might even have my specs in their computer. This is the most important component to the life of a rotary, don't skimp.
WWW.fluidyne.com