if you have a hatch back, do you have to use a box that is air tight with a vent tube to run at the track?
also, everyone on this forum says to use 0 gauge wire but the majority of the kits on summit come with 2 gauge and i see a couple 1 gauge.....why the difference?

 

yes you do unless you install a firewall to seal off the back of the hatchback from the rest of the passenger compartment.
if you do move the battery to the rear, you also must use a rear mounted master cut off switch which will shut down the electrical system when it is turned to the OFF position and the battery must be held down by at least two (2) 3/8" diameter threaded rods which are secured/bolted to the frame of the car.
the reason for the larger gauge battery cables is that there is a lot of current draw when starting the car and the longer cables cause more current drop to the starter which can result in hard starting, especially if the engine has a higher than stock compression ratio. the larger gauge wire, like 1 or 0 gauge will minimize the current drop in the longer cables so you don't have starting problems. if you have a basically stock engine, you can probably get by OK with the 1 or 2 gauge cables, just make sure the negative cable is just as large as the postive one (since it has to carry the same current load) and is connected to a good ground and that the grounding strap at the back of the engine is properly connected also. it also can't hurt to run the negative cable from the back all the way up to the block for the best grounding and easiest starting too.