Here's a good compilation of information regarding hot rod cooling. Read through it and pay particular attention to the paragraph "Cadillac Radiator Swap". The '76 was 552 square inches of core area. Swapping in that core support and having Ron Davis build you a radiator would in my opinion, be about as good as it gets. Others here may have varying opinions.
http://www.crankshaftcoalition.com/w...ng_system_tips
http://www.rondavisradiators.com/Welcome.htm