[Christ]

Smallest radiator possible with the highest cooling capacity available.

I think most of the pressure in the system comes from the amount of times the water has to change directions, not necessarily from the radiator. Measure pressure drop across the inlet and outlet of a radiator, at whatever CFM the fluid flows, and then do the same through all the passages of the block/head. I'm sure you'll find that it's much greater in the engine.

I had honestly considered replacing the radiator in my Civic when it started leaking from the end tanks (before I learned how to fix them) with some from a bike, which are much smaller. I never actually did it, but my Civic always ran over-cooled without the thermostat in it, and one of my goals was to be able to remove the t-stat and still have normal warm up times without overheating.