If you know what your bearing clearances are and you know what the oil temp is when you're racing then you have enough information to call around and get a recommendation. The tech guys at the oil places will want to know that information.

A lot of drag cars go down the track with the oil fairly cold so you need to use a thinner oil than if it was a circle track car that runs at full temp. But you don't want to go too thin if your engine builder used wider clearances for the bearings.

A 10W-30 should be a good compromise for most bracket type engines but you might want to go a little thicker or thinner depending on your conditions.

I don't think you really need a 20w-50 unless it is super hot where you race and you have really big clearances in the engine. You are probably putting a lot of drag on your oil pump and maybe damaging your engine running that thick of an oil. Especially if the oil temp is less than 200+ degrees when you go full throttle.