Well, as far as a feeder series, The Mustang Challenge feeds into GS Koni with identical prep cars. SCCA already has American Sedan.
As far as almost completely stock, you have the Touring categories under SCCA.
With the decline in motorsport series in general that aren't NASCAR, it seems unlikely that splitting efforts more would be a good idea. However, if you can get all the "good ol boys" behind it... who knows.
Maybe Speed will make a specti.. I mean series out of it. I don't think anyone watching that would be too interested in racing, however (good "tv").
- dow