For 135MPH and under,,, even though a roll bar/cage is not required (recommended) you still have to have certain driver safety equipment.
SA2005 Full Face Helmet, Long Pants and Long Sleeve Shirt (fire suit recommended) Boots and Gloves.
Seat Belt (factory 3 point OK) but SFI harness is better of course.
For over 135mph you will have to have Roll Bar/Cage and all SFI Drivers clothing.
Charles