so do you think the fpr or fc wire on the crown ecu would work to power the fuel pump ecu ?
If your ECU outputs FP or FC signals, then I think you have an older vintage ECU that just wants to see a fuel pump relay that switches a resistor in & out of the circuit to the fuel pump in order to vary its speed. This is a less reliable system than what Toyota/Lexus used on the '95 and later cars, and it will not work with the MKIV Supra's Fuel Pump ECU.
I think you could probably retrofit an earlier Fuel Pump Relay and Resistor to the Supra to make it work according to the earlier philosophy, or you could just feed the fuel pump through the main injection relay at 12v all the time, which is probably what you're doing now, right?