Roger,
We copied CSX3104 identically. The hubs on the rear of a comp car are almost IDENTICAL to the hubs of a street car. (The ONLY difference is the threaded portion of the knock off--where the wing nut screws on--is about 3/4 of an inch longer.) The face of the hub--the part that determines the track--is in identically the same place, both front and rear.
As the original cars had both sunbursts and the normal Halibrands on them, the wheel offsets are not the same---hence, the quoted differences in tracks you have seen.
As for what the original track is, I do not know. (I guess I could measure our original car.) Your problem with the literature is, of course, not the first time false data about the Cobra has been published. There are just so few of the original cars around no one really knows.
We have sold at least 40 suspensions to original car owners over the years. Of course, we have sold numerous cars to Shelby for he CSX4000 cars as well. One thing I do believe, though, is our car's suspensions are as close as anyone will likely ever get to the original.
David
