Radiator for 73 Duster B engine

Hi I'm putting a 451 that's about 640 hp into a 73 duster that was originally a 6cyl car. The rad opening is 23 wide and 16 height.The guy I bought it from put a 340 and somehow fitted a 26" rad and made new holes to mount the rad onto the support. But the rad is a single core with plastic tanks and had a hard time keeping the 340 cool.I would like to get a rad with electric fans but I'm not sure what size 22" or 26". I need the most cooling since this will be on the street and bracket raced. Also which brand ? Be cool, Griffin, Champion,ECP, US radiator ETC... This is my 1st venture into aluminum rads and want to get it right the 1st time. Some have told me that an Ebody 26" will fit nicely as well.
Thanks for your help I want to keep this baby cool