Clone Cooling

As you can see from my post in this thread, I have a bit of an "issue" with cooling my Dart. Size-wise, the radiator is as big as I can fit in the thing, the fans are about 13ins each and I'm running a Milodon waterpump with, IIRC, a 7in crank pulley & 5in waterpump pulley.
Grant it the engine is big, strong, high compression but I see guys running 800,1000hp or more on the street without an issue. Anyone have any ideas?