I am having a similar issue. I have a 1940 Ford on a Chevy S-10 Chassis w/ a 350 motor that has been on the receiving end of quite a bit of performance work. I was in an accident and don't have a whole lot of cash and need a smaller radiator.

Would that 3-row mustang radiator be able to cool 350-370Hp?

Yeah a stock SBC sure.... but with the extra horsepower?