If were wanting to swap my rear axle out so I could install say an ARB air locker or other TAD what would be my best options for doing that? I have heard of people getting custom Dana axles but where do you go? I mean I know they would have to put the spring perches in the same spot and match my 3rd member right? or does the 3rd member get replaced as well with only the original drive shaft remaining? And what about gearing? would they have to sync with front or would you have to swap out both?

Thanks for any help, I have searched all over for some sort of add on for this ride and that seems to be my only option at this point. But, can't find anyone who has done anything like that yet. I would like this truck to more than a beach runner but without a locker I don't see it be much for heavy trail use.

 When you do something of that kind of magnitude , you have a lot of thins that you need to keep in mind.
First, if you have a different rear axle setup for your truck you need to make sure that it has the right gear ratio. It has to have the SAME gearing that you have now, unless you change the front gears at the same time to match the rears. The brakes have to be adaptable, the control arm mounts and spring and shock mounts all have to be remade for the axle housing, and you have to figure out how to make the driveline work on the new diff.
I think you might have your work cut out for you to make everything work for you. You might just be better off finding a high mileage GV, maybe with a bad engine, and put the engine, transmission and transfer case in to it. Then you could easily build the GV.
Unfortunately nobody that I'm aware of makes a locker of any kind that will even come close to working in the XL-7. Sorry. I think you are better off leaving the thing relatively stock and build something else with the Suzuki nameplate on it.

Why not put a GV axle in it?  Gives you locker options, and should just bolt in ??

The best way to go would to get a 99 or 01 GV  axle.  And why a 99 or 01 because in 02 or 03 ?  the gv's started getting the xl-7 axle.
George

 WHAT??? Who fed you full of? The 02 and 03 rear end is a 99-04 rear end. Who told you they started to use the XL-7 rear? The current, 05 I beleive uses the 7.5" ring gear still. The XL-7 uses a 9", I think, might be an 8" or 8.5", either way, it is a completely different diff. I don't think you can use the GV rear in a XL-7. I think the suspension mounts are different, aren't they? And isn't the GV narrower than the XL-7? The GVs all had the same rear end, with the only exception being the diameter of the crosspins in the carrier for the spider gears.

The track width is the same between a GV and XL7.