guys the 7.35 wasnt a guess , its from the 2005 NHRA rule book so i wont debate it here ,
i assume the question was for a buick reagl so no convertible
from sportsman ,superpro and pro section 1A
ROLL BAR
roll bar mandatory for all cars (includng TTops) 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 une buggy type vehicles running 12.00 (*7.50) seconds and slower . permitted in all cars , see general regulation 4.10, 10.6 .
(*= 1/8mi et)
roll cage
roll cage mandatory in cars running 10.99(*699) or quicker or any car exceeding 135mph, in full bodied cars with unaltered firewall ,floor ,and body (from firewall rearward ,wheeltubs permitted) running between 10.00(*6.40) and 10.99 (*6.99), roll bar permitted , in convertibles running 10.99 or quicker or exceeeding 135 mph, roll cage mandatory. cars running between 7.50 (*4.50) and 9.99(*6.39) must have chassis inspected every three years by NHRA and have a serialized sticker affixed to cage before participation. there is more but it applies to dragsters..
the section in the roll cage allows for a 5 point roll bar to legally take you to 10.00 as long as you are slower than 135
section 4.10 in general rules details the 5 point bar (you dont need the passenger bar across the door area) and it must be attached to the frame on regals and to a 6" square by 1/8" plates (top and bottom) on the firebird
there are other safety items you need as well once you cross the 7.35 1/8th mark like an SFI 3.2A/1 single layer fire jacket , and SFI spec 16.1 three inch retsraint 11.49 (*7.35) and quicker , and a driveshaft loop even if you are only on street tires , if you run slicks the loop is required at any speed.
and at 10.99 (*6.99) or faster than 135 you need a tranny sheild and must have aftermarket axles with axle retention device (no c-clips )
also note for some NHRA competion classes classes like stock fuel injected you need a roll bar for competition if you are faster than 14.99 (A/FI through G/FI) and for stock eliminater its required for 14.49 and faster (A/SA through M/SA) and all convertibles require a roll bar