R-A Rules:
6.4.A.11: If a lead-acid (wet cell) type battery is located in the drivers/co-driver
compartment it must be equipped with leak proof caps and enclosed
in a non-conductive “marine type†box. Dry Cell batteries commonly
known as Recombinant Gas (RG) or Glass Mat Technology (GMT)
batteries are not required to be in a “marine type†box. The hot
terminal shall be insulated on all vehicles. All batteries shall be
securely attached to the primary structure of the vehicle.
10.2.C.14: The original battery and alternator may be replaced by another
commercial automobile unit of equal or larger capacity provided the
location remains unchanged. The make is unrestricted.
Section 10.2.C is specific to Production and Production GT cars, so if your car is in another class then you do not need a battery box in the passenger compartment for a dry cell battery.