Looking for info on 12 bolt posi

[bc72fleetside]

I have a 72 c-10 with trailing arm susp.
I have one tire fire. Is there a planetary
setup that I can get to go in my rear end to give me posi,like say out of a newer truck,or do I have to replace the whole rear end with a posi diff. I would like 3.55
or 3.73. Also I was reading somewhere about using mid 90's caprice calipers and
rotors with the coversion brackets. Is this a good route or is there a better way.
Any help would be appreciated,thanks.