I need the roller that runs inside the verticle rail in the front door for my 68 442 convertible with power windows. It basically keeps the window centered and the roller glides in the verticle rail at the rearward section of the door. I hope I am describing it right. I have found the quarter window rollers, but don't see anyone with thew other ones. Does anyone know where I can get one? Or, as luck might have it, is it part of the regulator itself?? I almost looks like it just pops on to a ball stud on the regulator. HELP!!