rear gears

[rioredstang]

I have all the tools at my shop. I own a auto repair shop so building the diff. is not a problem. I intend on having several diffs set up so at the track we can quickly make changes during practice sessions. I have a 4.08 and 4.36 set up on HLSD's now. I don't know if short or long or what size bolts but I will find out. What are the spec for short vs long? I would like to have a 4.6 and 4.9 also. I have not ran this car yet so I don't know the torque and rpm curves. This is why a need the gears to be able to match transmission ratios and final drive ratios to best suit corner speeds to each track. I would spend a lot of money to buy everything new so if I can find used parts that will work helps a lot.
I appreciate all the help, I value everyone's opinion very much. Forum's such as this are very helpful to newbie's like me. I have spent a lot of time with high horsepower V8's so the tuner cars are new to me.