Good luck, but I doubt they will make the custom. The Alumastar rears are a 3 peice wheel, and they just take a standard center and standard hoop sections to come up with something. Then again, I could be wrong...

You could just go with the 6 and get the rear narrowed a touch if it needs it. I know the place up here gets 90 to cut, narrow and weld the housing, and if you have aftermarket axles with C clip elims there is usually enough spline to cut an inch or two off and still have plenty left. Hell, if you do that you could actually get a few inches lopped off, and be one of the few that can run with a deep dish wheel.