Pick & pull rear ends

[Mrturner1]

So I'm knee deep into my engine build and the tranny is getting some love in the near future too. My rear end is stock, and does awesome show stopping 1 tire burnouts. My question is, how do I determine exactly what rear end I currently have AND, is there a rear end I could search for at pick & pull that has a posi and something like 3.42's or 3.73's? My truck is a half ton long bed, if that matters. I'm only limited by my lack of torch or welding capabilities, other than that I'm getting pretty handy with the wrenches.

Also, I'm doing this to avoid taking my truck to a shop and spending 1500 bucks on a posi and ring and pinion. If a swap is really hard or requires welding I can have my rear end rebuilt, just thought to check for easy swaps first