I've had a gze in mine for almost three years now running a standard radiator and single thermo (12in i think) and front mount. I have never had a problem with the car overheating. I live in sydney and am frequently in stop start traffic. I sat in bumper to bumper traffic yesterday arvo for over 40mins and it idled away fine the whole time.
Although if you are planning on doing trackwork or spending a long time on the dyno you may need to upgrade to a bigger radiator and/or fit and oil cooler.