Tire rub on 5-7 drop

[RaceProMarketing]

1983 C10. The truck was dropped when I purchased it and needs some serious upgrades ... but ... I was surprised that the only tire rub I have is on the right front when making a medium-to-hard left hand turn.

I assumed that the tires (245/50/20s) were rubbing the fender due to a bad spring cut or some other crazy reason. But I recently put an aftermarket bolt-in battery box in the the truck (the original was about to fall out), moving the battery forward about an inch and up about an inch. Now the rub is much less significant and I am positive that it's the tire hitting the battery box. I can possibly raise the box up another 1/2 inch to 1 inch.

Has anyone else experienced this problem? Is it common to have to relocate the battery? I am 98% sure it's a 5/7 drop, but because I didn't do it, it's difficult to tell. There are no inner fenders (not much of anything in there actually). So what kind of trouble will I encounter if I decide to put inner fenders back in the truck.

I drive it daily and hate getting the sand/dirt/water off the road in bad weather.

Thanks.

Robert--