Offset wheels will do essentially the same thing...if the point of contact on the tire with the ground is farther away from the knuckle then there's more stress.
http://rcjuice.com/Basher-Series/Juicepax-Basher-Series-5000mah-3S-11-1v-30C-45C-LiPo.html
You'll have to wait for it to get back in stock. Sometimes you can find them on ebay
That gearing's a little tall for an xl, I'd drop that bell down to a 16t.
Savages don't really need upgrades....they're good in stock form.
Really the best areas to upgrade are the electronics