Hi, no, I know of no rule for unaltered stock fuel tanks.... maybe in the stock class...
moroso, or comp engineering makes a sump you can install on any stock tank, ......but get a gas tank repair shop to install it for you.... gas fumes and sparks or flame tend to cause the air inside the tank to expand very rapidly.... :shock:
It may be more cost effective to just install a fuel cell, they are a little safer and look nicer.... summit sells some nice aluminum cells at a decent price.