stock or different rear axle

Can i use my stock axle to install airbags and lay my truck on the ground? if not which axle would be best to use on standard cab Mazda b2200

Yes you can.

You can, but you will be limited to a high offset wheel that tucks enough so they don't rub the bedsides. Good luck finding high offset (+31 and more) in a 6 lug. They are far and few between aftermarket choices.

pick your wheels and build around them. if you need a narrower rear then nows the time to swap it'

What would be a good transplant rearend to use?

Toyota is a super popular swap.