When moving the battery to the rear of a third gen camaro and you plan on running it at the track I know you must have a sealed and vented battery box. If you have a dry cell battery, such as an optima, do you still need the sealed box to pass tech?

Yes and it's a constant complaint with NHRA rules. All batteries must be isolated from the drivers compartment including Optima batteries.

Does that also apply to IHRA?

yes

what if you have the plastic panel that goes over the spare tire compartment bolted done like stock and the dry cell in there?

General regulations 8:1

All batteries must be securely mounted. Rear firewall of .024" steel or .032 aliminum required when battery is relocated in trunk. In lieu of rear firewall, battery may be located in a seal approved box. If a box is used it must be vented outside the body.

Buy a rulebook! You either need to install it in an approved box or fabricate a proper rear firewall to isolate it from the drivers compartment.

i've been pretty lucky through tech and never had any problems.............until now probably.