If you think you really need one, then a 13 row will be fine or even a 7 would do. IMO of course.
But I really wouldn't bother.
Do you run a cooler on your race car Tony?
We didn't until this year, but we have one of those cup racer ones, think it's off a Ren 5.
It has the coolant runing through it, so it warms up quicker, it looks like a sandwich plate with two hose connections coming off it.
I'll try and find a picture.
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