Oh, I see you DO have a '93 Cobra... well you can figure out backspacing yourself... I'm just trying to think of how that was done... it involved flipping the wheel on it's face, taking a straight edge and laying it across (this is where can't remember) either the outter or inner lip of the wheel, and taking a tape measure and getting a measurement from the surface that gets bolted to the rotors to the edge of that straight edge.... and I can't remember then if that's the number to use or what?? I know I'm close...
that is how I get the backspacing for my '69 mustang, but the newer wheels are goofy numbers. the cobra R's i have for it are a -36 backspacing. I think that means they are -36mm from the center but when i measured then (how you described) and converted to english the numbers don't add up, maybe it is cm, I'll try that now. I thought someone might know the (-) offset value ford used on the original's.
Out of curosity why do you want to know? If it is so you can buy another set wheels I think you will be out of luck. I am 99.9% positive nobody makes a aftermarket wheel to fit the 93 cobra.
actually i'm looking into getting a set custom made or modifying a set of 17x9 Cobra R's i currently have. I want to run 275 tires on the back. so i need a custom set of wheels to get them to clear.