I would use as close to stock size as possible. I'm most worried about the small size of the thermostat to radiator, and radiator to water pump. If anything I would have gone bigger than stock. you are running 3-4X the horsepower, you need as much flow thru that radiator as possible.
Droste Drummer. Droste like Frosty.
00" Red ZX3: Volant, ported throttle body, titanium wrapped SVT header, 2.5" exhaust, Magnaflow res/muffler, FR UDP, Mac cam gears, Lowered 2", Koni's.