Right now I'm looking at a complete rear assembly(8.75, tru trac, 3.55 gears) that will get me to 5 x 4.5 bbp including rear disc brakes for about $3250.
That seems excessive to me. If you shop wisely (and take your time), you should be able to accomplish that for much less.
I built my own 8 3/4 rear diff, with suregrip, 3.55's everything brand (I rebuilt the suregrip unit) new for a shade over 600 bucks. I could add disc brakes for another 400.
