I assume that "I" meaning International rail spacing and 32 / 30 meaning 32mm dia or 30mm dia. So is that what your wanting or do you want American spacing and size?
The difference is in center to center of the tubing. Most karts now days are international spacing. I make my butterfly's capture the outside rail and float the inside rail. That way they'll work on either. If you need butter fly's Bob just hollar we can make what you need.