472 Hemi in a 68 cuda ,cooling problems

I have a 68 cuda with a hughes engines built 472 hemi and a 727 auto with a 3000 stall converter.it was originally a 318 car and has the original 22" 3 core radiator with shroud.it has a 6 blade flex fan and a 1" spacer 180 thermostat.on the hwy it's fine.idling or in traffic.it gets real hot.do i need a different radiator and fan combo?or what do i need to keep this beast cool?