Steve, why can't I use a different type of battery. I don't see anything in the rules that dis-allows it: What am I missing?

GCR:
9.3.9. BATTERIES
Battery location is unrestricted within the bodywork (except Showroom
Stock, Spec Miata, Touring, and Improved Touring). If located in the
driver/passenger compartment, vented wet cell batteries shall be in a
nonconductive marine type container or equivalent. The hot terminal
shall be insulated on all cars. All batteries (on-board power supplies)
shall be attached securely to the frame or chassis structure independent

of the marine type container.

IT Rules
9.1.3e
Batteries may be replaced with those of
alternate manufacture provided they are of similar amp-hour

capacity and weight and are fitted in the standard location.