This sounds like a core support or duct work would help you a lot. I've found most of the time cooling problems came from letting the air go around the out side of the radiator instead of forcing it to go threw it.
Fans are for when your sitting still or going slow.
I'd bet if you stopped any air entering the front from going around or under or over your radiator, that even a skimpy one would be ok for a drag race.
There are exceptions, like pushing water threw too fast or slow or backward, but most times it's not forcing the air threw at speed.
If your driving it on the street a radiator with more capacity may be needed because of slower air flow. That just allows most of the water to stay in the radiator longer and get cooled.
PS you want air threw all the fins , don't block any or run tube type ducts, and think your getting air. Been there , Ouch I made a shroud for water pump type fan that was very flat against radiator with tunnel for fan. It didn't use the outside corners of the radiator then. When you add them corners up they make up 1/3 of the area.