Easy-fit oil cooler kit(s).
350 to 400ftlb = OE temp-stabiliser + stat + 1 x cooler.
400 to 500ftlb = OE temp-stabiliser + stat + 2 x coolers + A650E sump.
500 to 600ftlb = OE temp-stabiliser + stat + 3 x coolers + A650E sump + remote filter.
With a thermostat fitted it's not possible to over-cool, however, fitting an ATF temperature gauge is the sensible way to learn reality of cooling required!
Big Sump Mod here. http://www.mkivsupra.net/vbb/group.php?discussionid=207&do=discuss
Temp Gauge Mod here. http://www.mkivsupra.net/vbb/group.php?discussionid=210&do=discuss
http://www.ebay.co.uk/itm/8-Row-Aluminum-Remote-Transmission-Oil-Cooler-Auto-Manual-Radiator-Converter-BK-/152365524315?hash=item2379b1655b:g:s4sAAOSwA3dYW2zt