Well, if you could find one of the modified PS32 boards for one-gauge, those were beefed up with a heatsink on the motor driver FET, that would probably be one to try if you wanted to swap boards.
If you want to stick with the PS/2 board, adding a heatsink to the driver FET, even if you have to dispense with the plastic carrier, might be a smart move. I'd also make sure the bridge rectifier has a GOOD heatsink, perhaps a custom one with a better bond to the chassis. Those are the two high current critical components in the motor drive circuit.
Truthfully, I think just blowing air on it with a tiny fan is going to be a lot less effective than better heatsinking. Adding the fan as well can't hurt...
