ive used gemini ones before, they do suffer from heat soak in trafic on hot days but what doesnt with no thermo fan.
I picked up a 1960s bluebird radiator from a club member modified to fit his sprint car, just giving it a clean and pressure test but thicker and a litlle bigger than stock but not as wide as gemini one. its 3 core to i think.

Gemi is good though on a15.