What gauge sheet metal

I replaced my rear frame rails with 2x3 and now i need to fab everything from the torque boxes back i got wheel tubs and i know nhra will exept 24 gauge sheet metal iv been using 22g to do some patch work and it seems thin to me so my question is what gauge SM would you guys use for the trunk floor and rear hump im leaning to 20g but any advice would be great if anyone has some pics of there SM work in the back halfed cars that would be good to the car is a street/strip car more strip than street

I think factory was 19 gauge, but I do not know that for sure and would also like to know the correct answer.

I agree, I replaced all of mine and used 2x3x1/8" frame material. I used 20ga for the whole flat trunk floor and the flat tub sides, 22ga for the curved tub belts with a pittsburg seam to join them.