How much roll bar or cage is needed for 10.00 & slower

Chromoly has an advantage because the cage can be built out of thinner (and lighter) tube and be just as strong. Be wary, however, as it is difficult to weld properly. Overheating can make it brittle and liable to crack under stress. I honestly wouldn’t recommend it unless your builder has experience with it. Fabrication mistakes will more than outweigh the material’s advantages. The nhra hasn’t caught on yet, but there’s a type of mild steel being produced now called docol r8 that’s stronger than DOM but much easier to work with than chromoly. Docol® Tube R8 - A.E.D. Motorsport Products

You have to look closely at the regs concerning your class. The nhra has different tube requirements per vehicle weight that in themselves can really add some weight.

1.75” steel at .095 wall thickness weighs 1.68 lbs per ft. It generally takes about 100-150 ft to build a cage depending on the car and how crazy you want to go, which works out to about 150-200 lbs. This is actually less than 1.5” .120 wall tube (1.77 lbs), which a lot of people use. Chromoly tube of similar strength would be 1.75” @.083 which is 1.48 lbs/ft. This is a .2 lb weight savings per foot of tube, which adds up to a 20 lb weight savings for a 100 ft cage. Maybe just skip lunch.