Your questions can't be answered properly. What kind of truck do you plan on using? Long bed? Short bed? How much truck you have is also going to have lots of opinions. I have a 34' 5th wheel that has a loaded weight of just under 10,000 pounds. I tow it with a Ram 3500 SRW gasser with the 6.4L Hemi. It does just fine. I can get up to around 4,000 RPM's going up steep inclines and for some that's annoying but for me it's no big deal. I don't lose any speed and I'm not always going up steep inclines! Don't even consider a half ton pickup with a 5th wheel. You'll have payload issues. Yes, 3/4 ton, 1 ton and bigger trucks have stiff suspensions and have rougher rides but they aren't terrible. You get used to it quickly. Many more will chime in and give their opinions. Provide a little more information so they will be able to give you better information in return.