They are probably pretty much all the same. I just installed a RB25DET in my 32 GTS4, and the only difference was in the top radiator hose.
It's probably best to get the radiator that comes from the same car as the engine - can't go wrong with that.
Are you sure it's the radiator? Import engines have a tendency to blow hoses anywhere on the engine, because the Japs don't take care of their engines, and don't use coolant in the cooling system.
For your overheating problems, you need to build some sort of undertray to:
1 prevent the air going down in front of the radiator and out under the car
2 draw the air out of the engine bay so that air has to come in through the radiator.
You could also re-wire the little thermo out front of the A/C radiator so that it comes on when you activate the A/C - presently, it's probably activating thermostatically.