What it comes down to,.. is...
Originally, you asked about swapping to a new wheel... and you'd never done this before...
Answer:... It ain't easy...
Now, you're machining parts for the hub,... changing wheels, and converting from a drum to a rotor... and going to chain drive...
You are either so naive that you have no idea...
..or, your original question was a herring...
If you can do this, and think it's worth the bother... do it...
If you are dreaming,.. stop it... it ain't goin' to go like your dream...
I would keep in mind, that rear braking is less than 30% of total braking potential, and a Savage doesn't have that much potential to start with... so rear is more like less than 10%...
So,.. a rear disc, is basically cosmetic... as is a wheel change...
..(a taller wheel will just require a narrower and lower profile tire,.. negating any significant geometric change)...(a few more tire options at 16" and 17", but, again, basically cosmetic)...
Unless,.. you're also going to redesign the swingarm...
Mostly,.. an exercise in "differentness"...
Metal masturbation...
...
If you try it... take pics...
If you're really a newb to this... take video too...
We'd love to see...
..