I don't think there will be a problem with the location, just make sure you use big enough wire. I've relocated batteries in several vehicles including 4WD's and SCCA race cars with no problem. First, use a brand new battery, you don't want any nasty fumes in the cabin of your rig. Second, use 4 gauge wire, you can pick it up pretty cheap at a welding supply store for a lot less than you might think. I think I paid something like .60 cents a foot, plus when you get welding wire its a lot more flexible so you can jam it around corners and in tight places. I can't stress safety enough, make sure you mount the batt. box securely and about once a month inspect the battery to make sure there are no leaks in the cabin.
Never trust a man in shiny shoes or a clean hard hat.
95 ZJ-Daily Driver (bad on gas)
09 Genuine Roughhouse 50 scooter-Daily Driver (good on gas)