Well, if im not mistaking, some model of ford probe has gearbox-cooler as standard equipment, might be a good start looking for a pump! Otherwise get in contact with any company dealing with gearboxes, these should know what to use for your gearbox!

Another thing i forgot to mention is the fact that you should use some kind of oil thermostat so that the oil in the gearbox is not getting too cold! Check with burton power for these as an example! www.burtonpower.com