Mike hit a lot of the good points, Ive done them on my car and a few customers there are many ways you can go.... The car can handle a little different with a lot of tire under the rear.
Pricing is 110% depended on what you do, rear end, shocks, etc...
What is the purpose of the mini tub for you?
My own rear, shorted about 2.5" per side, 9" ends, Wilwood disc brakes, 15" x 12" 6.5" backspace, Autoweld Chassis direct fit mini tub, Strange Hypercoil double adjustable shocks and springs, 33 spline Mosers, 5/8" stud, star flange and gun drilled, spool, blah, blah, blah....
Its easy to dump $1500 in the complete 8.8 with 9" ends (which is my recommendation since c-clips elims no matter how good you do them eventually leak, if your building something like the above it makes no sense to not go 9" ends). I have the fixures to put the 9" ends down, narrow the rears etc... Then you need to consider brakes, they have to be determined BEFORE you do the rear!!
Autoweld sells the direct fit tubs for $119, if you need the shock bar and brackets (I just custom fab this) Team Z sells a complete kit in the $320-340 range. At that point I also needed offset
lower control arms.
With the stock length rear most guys run a 15" x 10", 6.5" backspace.
If you need anything let me know if I can help.