I used a Champion HD radiator and their fan/shroud on my mild 340 Formula S (maybe 350 HP). It cooled OK much of the time but was not adequate as temps rose above 90 degrees. In Denver, air density is lower so more air flow is needed for the same cooling need. I don't think the Champion fan had the needed CFM for my application. Also, RRR said, Champion radiators mount further rearward taking up space and you many not have with a '70+ long snout water pump. I ran out of room with my setup (many reasons for this including undetected front-end damage that move the core support back about 3/8"). I went with and Engineered Cooling Products dual fan setup that allowed the water pump to be inbetween the two fans with enough room. Even a 7 blade factory fan didn't fit, so I had to go with electric.
the ECP radiator (22") keeps my 340 between 180 and 200 at 95°, so I am OK with that.
Honestly, I should have used the '69 and earlier WP setup as it has much more clearance (3/4" shorter snout) allowing a factory fan.
As RRR said, this is hot rodding and your initial setup may need to be modified or trashed to make the system work. Not cheap, but you learn from your mistakes.