
^
you can get crazy with all of them if you wanted to:
-oil cooler
-tranny cooler
-ps cooler
-diff cooler (s15 style)
but i think you'd only need an oil cooler, even on a hot track day in florida. maybe a power steering cooler if you were going to do non-stop auto-x or drifting runs without any breaks, but i havnt heard of anyone's stuff going bad yet because of that.
350z's have power steering coolers IIRC, there was a discussion on freshalloy about retrofitting into an S chassis' PS system. i'd bypass that loop on the DOHC PS lines that goes over to the passenger frame rail and back, and throw the cooler inline with that.
for an oil cooler, there are sandwich adapter for $40 from greddy and such for KA's and SR's, some companies even have total blockoff plates for the whole oil filter housing on SR's with a pressure sensor hole still and dual -8 or -10AN outlets...pimp.