Just read the NHRA rules on this topic. You must have a firewall separating the trunk area from the cabin to avoid using a vented battery box.
Firewall can be made of aluminum or steel (different thickness requirements) and the the battery hold downs must be 3/8" dia min and if it uses J hooks they must be welded closed.
The important thing I got from it was a few inexpensive pieces of metal to make a firewall would allow more flexibility in the battery mounting area (plus look cool if I get a couple sheets of stainless through work)
Don't forget your exterior activated kill switch if you're trying to pass NHRA tech! It must be labeled and must kill the car. Haven't decided how to wire mine yet so the computers and radio don't get their power cut but the car dies instantly. I don't want SAFC settings, fuel trims, or my radio presets disappearing all the time!