I'm sure a diesel pusher would have a much easier time, but is it even worth considering with a gas unit?
Part of the question is if you are shopping new or used? It is much less difficult to find the specs on new models because the manufacturer websites will list all of their models. Since we have no way of knowing how much your coach will weigh when ready to travel, the best figure of what you can tow will be the GCWR less the GVWR. If you look at the website for
Winnebago you will find that coaches in the lengths you specify only come in gasoline chassis and they have a GVWR of 18,000# and a GCWR of 23,000# for a towing capacity of 5,000#. Even if you look at their largest diesel RVs they do not have a 5,500# towing capacity unless you load the RV well below it's GVWR.
Tiffin does have an Open Road that has a GVWR of 26k# and a GCWR of 30k# so it would have the capacity you need and is available in 32' and34' lengths on a gasoline chassis.
Newmar gas coaches are built on the 22k# GVWR chassis so most likely do not have the capacity to tow a vehicle of 5500#.
Although you will see trucks and other vehicles of similar weight or more being towed by many motorhomes, the design limits usually are not as high as the towed vehicle weight of the heavier vehicles until you get into the highest priced diesel coaches like Foretravel or Entegra, or similar priced diesel coaches. They often argue that they tow a heavier load that rated for just fine, but the issue is not moving it but it is what you can stop or control on a steep grade, in bad weather or in an emergency. It is about what will happen with a child darts out in front of you from between parked cars. Will you stop, or run over him?