Re the Ford V10 - I wouldn't hesitate to get the 5 speed transmission. It was a big improvement over the 4 speed. And, I would also suggest getting a 5 Star Tune if you purchase a 4 or 5 speed transmission rig.
As to quality gas motor-homes, my answer is Newmar, Tiffin, or Winnebago/Itasca. I have to say I'm really impressed by our 2012 Newmar. The overall insulation is very good...we've been very comfortable in some mid-teen temps with the propane furnace doing its job. Also, there's enough heat diverted to the fresh water bay to keep the water flowing. Because of their wall design and double pane windows (at least on ours), the interior is very quiet. Ours is just shy of 34' and I will tell you that in very hot temperatures, you need two AC units.
Good luck on your search! If I can answer any questions, just send me a PM.