Not an SCCA rulebook but maybe this will help? This was the only reference I could find on google in relation to side bar spacing
5. Doors and Door Reinforcements:
Â· We will allow almost a cage built around the driver from sturdy, easily assembled material bolted to the
car body ONLY. Bars may be welded to each other.
Â· As a minimum the drivers door MUST be reinforced with 2â€x6â€ Channel Iron, 6â€ I â€“Beam, or 2â€x6â€ Box
Steel. 3/16 minimum thickness for a maximum of 76â€ long.
Â· Ends of the bars must be chamfered, beveled, or rounded.
Â· Door bars must be bolted ONLY with a minimum of four (4) Â¾ â€œ bolts through the entire door/doorpost or
fender with a good size washer.
Â· Door bar can extend 8â€ maximum ahead of the front fender/door seam.
Â· Placement of bolts; Beware of driversâ€™ movement inside vehicle.
Â· Remember, if this bar falls off â€“ you are automatically disqualified from your heat.
Â· All doors must be bolted or chained. Bar clamps are acceptable.
Â· Doors MAY be welded. There can ONLY be a 5" stitch and then 5" space between the next stitch.
Â· Passenger door bar attached in a similar way as above. This bar is optional.
Â· Cross bar behind the drivers seat is strongly recommended.
Â· Head rest optional, but MUST be secure.
Â· It is also recommended that the bars door and the steering wheel be padded around the driver.
Found herehttp://www.trianglehall.com/4-6%20CYLIN ... ations.pdf