Cameron,
I am running a commodore (
VB/VC V8) 3 core radiator on my cleveland and it works fine. The recent 40°C days I drive from the Picnic at Hanging Rock all the way through Melbourne in traffic with no issues.
Air flow is the key. Make sure your fan is large enough. I would suggest you install a by pass switch on your fan from the thermal switch for hot days and traffic, you then have full control on your heat.
Regards
Tony