Mr Google search brought up this NHRA info. It's a few years old...
All batteries must be securely mounted and may not be relocated into the driver or passenger compartments. Rear firewall of .024-inch (.6 mm) steel or .032-inch (.8 mm) aluminum (including package tray) required when battery is re-located in trunk. In lieu of rear firewall, battery may be located in a sealed .024-inch (.6 mm) or .032-inch (.8 mm) aluminum, or FIA accepted poly box. If sealed box is used in lieu of rear firewall, box may not be used to secure battery, and must be vented outside of body. Strapping tape prohibited. A maximum of two automobile batteries, or 150 pounds (68 kg) combined maximum weight (unless otherwise specified in Class Requirements) is permitted. Metal battery hold-down straps mandatory. Hold-down bolts must be minimum 3/8-inch (9.53 mm) if battery is relocated from stock and other than stock hold-downs are used ("J" hooks prohibited or must have open end welded shut.).
This is the 2017 IHRA rule on batteries:
All wet-cell batteries must not be relocated into the driver or passenger compartments and must be securely mounted. A maximum of two (2) automobile batteries are permitted of 150 Ibs. combined maximum weight. Plastic battery hold-down straps are not permitted. All relocated batteries must be secured with a minimum of 2 3/8" diameter bolts or rods. When relocated to the rear of vehicle, the passenger compartment must be protected by a“firewall” consisting of a minimum of .024 steel or .032 aluminum. A switch must be connected to the positive side of the electrical system and when de-activated shut off all electrical functions in the vehicle.
Originally Posted by CrucialProspect
As for the venting part, is that as simply as a hole, or does it need to be baffled?
To this question I would read the rules as the box must have a vent tube that vents to the outside of the compartment the box is mounted in. A simple hole in the box won't do it unless maybe the hole is in the bottom of the box and is sealed and vents to the outside of the car.
Is your car a coupe or a hatch? If it is a coupe, just put a full firewall between the truck and passenger compartment and call it a day.