I just went through making my battery relocation NHRA legal. According to the 2006 NHRA rulebook, you don't need a battery box if you have a .024 steel or .032 aluminum bulkhead (including package tray). Otherwise, you have to have an NHRA-approved poly box or a box made of the above steel/aluminum, and it has to be vented outside of the car. This is in addition to a battery cut-off switch that cuts not only the battery power, but also the alternator feed. Also, you can't use J-hook type battery hold downs, and it has to be 3/8" min diameter, and you have to use metal to hold the battery in place (no plastic or rubber).
Whew. Lots to do. My set-up is an aluminum bulkhead, some 7/16" threaded rod, a steel 1" strap to hold the battery in place, no box, and a battery switch with an extra post that cuts the energizing wire on the alternator to kill the car when switched off.
Whew. Lots to do. My set-up is an aluminum bulkhead, some 7/16" threaded rod, a steel 1" strap to hold the battery in place, no box, and a battery switch with an extra post that cuts the energizing wire on the alternator to kill the car when switched off.