im not sure what you mean by one of the fans being two speed...i was under the impression that ford sets the ef fans up to both run low and high speed, by some switching that runs them in series for low speed and then in parralell for high speed.
i have EF fans in my car, i bought a davies craig switch to start off with, and set them up to both come on when the temp was high enough, with only 1 fan coming on when AC is on.
then i heard about some switches you can get from EBGTXR8 (i think thats his name?!?!?) and i got one that goes on at 95/off at 87 and also on at 105 and off at 92 (i think thats the temps)
i cost about $70, thats including postage and everything - he is in perth im in brisbane.
what i thought of after i had bought the switch though, if you wanted to spend some time researching you could use temp switches from a pre-computer controlled front drive car, something from the early 90s late 80s, just find out what car has a thermofan that is switched at the temps you want and then go to the wreckers and pocket one.
maybe a telstar or something...would be cheaper and neater if you drill and tap a switch into your thermostat housing then using a crap davies craig switch, they leak all the time.
you need to get a really cool thermostat though, i got one from repco thats about 82 degrees, if you keep the standard one it 'fights' the fans and you engine temps see-saw really quickly, not good for preserving your head gasket.
the switch i got was massive, too big to put in the housing, so i got a EF thermostat housing and top hose, cut the hose and got a piece of exhaust pipe, cut and flared it, then drilled and tapped a hole, fitted the switch and siliconed it in. doesnt leak (if you do this remember to flare the ends of the pipe or the hose doesnt stay on!)
here is a pic of what i did, taken from the back of the engine bay looking forewards: