i used a set of EL thermofans, they fit straight onto my radiator, i hid the relays under the coolant tank.
get a thermoswitch from a front drive car that is pre-EFI, they have thermoswitches on them already, should be cheap, you just have to do a little research as to what temp you want to run the car at. drill and tap the switch into the thermostat housing if it is small enough. if you want to get tricky use a two stage one, i have one from ebxr8gt, he sells a few differnt types. this way at X temp one of the fans come on, then if it still gets hotter then at Y temp the second one comes on. it keeps the engine at a steadier temp then if two of them come on at once and cool the crap out of it very quickly, which i believe is bad for head gasket longevity.
the one switch i got is bloody huge, i had to get a piece of exhaust pipe (clean of course) drill a hole an tap it to fit, flare the ends, then cut the radiator hose in half and fit it in the middle. i already had put an EF thermostat housing and top hose on my car so it was an easy fit. remember to wire up the fans so at least one of them is on all the time whenever you have the A/C on, otherwise your A/C will be crap. if memory serves me correctly the wire which operates the A/C compressor is green with a yellow trace. dont know about the V8 one though, but its easy to find, look at the firewall in the engine bay on the passenger side near the washer bottle, you will see a block of metal with a few pipes sticking out, and there ahould be two wires coming out of it.
get a multimeter and find the one that has 12V whenever the ac is on, not the one that cycles on and off with the compressor, and use it as your trigger for the fans when you turn the ac on.
here is a pic of my switch, taken from the back of the engine bay looking forewards: