Is it me or are dealers not stocking what seems to be to be a pretty basic request. We are trading up from a 2004 2500 4x4 QC to a 3500 QC to pull a larger fifth wheel. It's easy enough to find one with the basics: dually, QuadCab, SLT, auto (wife drives too and insists on this!). But I also want the anti-spind diff. and 4. 10 rear to get the most towing ability and my local dealer can't find any with the anti-spin and 4. 10 combination so I will probably have to order. Does anyone know why that combo is so hard to come by? Or am I missing something?