Champion radiator - I cut her open

You don't need a double pass radiator. You don't need 4 cores.

2 cores of 1 inch each will cool well over 800 HP if and this is the big IF, the water pump has the ability to keep up, and you are turning it the right speed.

2 cores of 1.25 inch would be even better.

No reason to ever use a 4 core. You need FLOW.