The switch is most likely as said a cut out switch to try and stop pikeys, though this is the first place they'd look, can simply cut the earth to the ecu and then no fuel pump or sparks, just starter.
Std means standard as in a standard switch fitted by ford, which as said this is not.
Yes 4wd sierra badges and 2wd different.
If a cossie is maintained right just because it's old doesn't mean it can't sit in traffic, if correct will sit idle all day long without problem.
The two most vital things apart from servicing are a new fuel pump loom and a new fan loom, the fan loom was crap to start with, made worse by the choice of temp switch used by ford as it had such a high hysterisis(span) used to make fans stay on so long that fuses/fuse boxes/wire melted!!
Getting too hot to touch is normal, I certainly couldn't without pain keep my hand even on the rocker cover after using the car.
tabetha