I run the Ford 8.8IRS set up in my Cobra.
I have the torsen LSD set up in there as well. I also sourced beefier shafts from a mob, as well as a few other bits from memory. They list ratios up to 4.56 and 4.88, about 1/4 of the way down the page headed
8.8 IRS Pumkin WITH 4 1/2 INCH BOLT CIRCLE
Brake Rotors Drilled and Slotted,Hawk Performance Brake Pads,Car Brakes,Brake Drums, htcracing
http://www.discbrakesrus.com/axles.jpg
My cobra actually twisted the frame where the diff was held in and then the bolts pulled through and diff moved up. The thickness of the metal used in this area was 1.6 or so, now 5mm plate from memory and handles 400+kw at the wheels.