Bobi,
This is a long answer but there is info here others too might find useful. Yes, that is the correct distance for the Corvette rotor and caliper, but that is a poor rotor and caliper selection in my view. The one piece rotor and hat limits your spacing options, the rotor diameter is only correct if you use the stock Corvette wheel size which eliminates 20" wheels or 15" on a Countach, your selection of master cylinders is limited and may have to deal with a booster and ABS, and finally it is just expensive. I cannot find a single upside to Corvette brakes. For the price of just the Corvette parking brakes you are halfway to the price of an aftermarket system like Wilwood. With a separate hat and rotor, you now have options on offset, rotor width, and rotor diameter, which now allows you a much greater wheel selection. Also the master cylinders are simple, economical (about $40) and tailored to this system. Attached is the suspension drawings for my new aluminum composite monocoque kitcar chassis and they show a one piece billet aluminum hub. I used to do them in steel, somewhere in this Forum is the article that I wrote for Kitcar Builder about that, but I have found the billet to be easier and cheaper in the long run. What I want to show you is the separate bracket for the caliper and parking brake caliper. That way I have one generic upright and I can tailor a simple bolt on bracket to suit any offset or rotor diameter that a customer may need for their particular circumstance. The realistic hub offsets are .41, .56, .71, and .81., and I can use any rotor diameter and width. The arrows drawn on it show the assembly. Either way you do it, do what Jim said to weld it, but take it one step further. Instead of cardboard shims, use two fittings, one that threads to your caliper mated to another that has an air hose fitting, and make a $5 adapter. Align everything, shoot your caliper full of air, and weld it. Keeps it dead nut through the cooling process too.