Originally Posted by 24-7
All cars with an OEM frame must have rool bar attached to frame
Cars without frames use 6'' square 1/8'' steel plates on top and bottom of floor, securely bolted together with at least four 3/8'' bolts, or top plate welded to rocker sill.
- NHRA 2006 Rulebook, Section 16, Paragraph 4:10
Huge thanks, especially for the Section and Paragraph number. I spent hours digging through the NHRA rules online and wasn’t able to find that info.