Hello gary & welcome.
No doubt - the length's you mention are not going to get you into a lot of older, smaller C.G's.
Friends of ours tow a 37 ftr with an MDT - they are limited to some C.G's.
You don't mention where you are, or what type of camping you do, so it's very hard to generalize.
Our coach is 32 ft and we have had a few probs (especialy in older C.Gs with "short sites" and "sharp corners" - we do have an long box F350 and are 50ft oal.
That being said - there are many newer campgrounds that can handle "Big Rigs"
You really will have to search for the sites you can easily access.
Hope this helps.
Y2K FORD F350 PSD,SRW,Longbox,CC.