The outside diameter of the rear axle flange on mine is 6.065".
I looked through available hats and saw most limited to a 5.750 od flange. You also need to get close on the depth of the hat as well.
With all the offsets with seperate hats and rotors, you need to get in the ball park in order to mount the calipers closely enough and preferably in order to shim them .
This is all doable but going in blindly is going to wind up with a lot of non-returnable extra parts.
Also, In this case it probably doesn't matter a lot but the GM rotors are $45 each but the commoness of a rotor for future replacement purposes would be preferred.
A friend gave me the name of a rotor company that will make anything for you. This guy restores classic race cars and this company is really the source of NASCAR components like brakes.
That is all well and good if you have a budget of $300 to $400 per rotor?
I believe that the front DT studs will work in the back when swapping the rotors to the outside but there are metric studs available in different configurations for race cars. The studs should not be the determining factors.