2013 rule book says..this is for bracket racing.

ROLL BAR
Roll bar mandatory in all cars (including T-tops) running 11.00
(*7.00) to 11.49 (*7.35), in convertibles running 11.00 (*7.00) to
13.49 (*8.25), and in all dune-buggy-type vehicles running 12.00
(*7.50) seconds and slower. Permitted in all cars. See General
Regulations 4:10, 10:6.

Tony

70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)