I pulled a 49' goose with a TAD and 2 spare engines,2 spare trans and hundreds of clutch disc. Lot's of tools, 100 gals fresh water, engine changer and tons of other stuff. My dually would not do it, it messed with the computer on my dually it was so heavy.

300 HP is not enough imo for a big truck or RV to pull a trailer.

So I bought this used with 4400 miles on it in 2002.
FL112 cab which allows the big engines, It has a special order RV C-12 Cat with 505 HP and a double over drive full auto trans. It's a dream to drive with ton's of power and get's better fuel mileage than my dually got. 200 gals fuel =1700 miles.
It's a 16' box which is big enough for 2 of us. It has everything that a RV has including 125 gals of fresh water and 2 holding tanks to match.8KW diesel genset, the works. We have stayed in it for up to 2 weeks at a time.

I can take it anywhere, any parking lot, any campground with my open trailer. Can't do that with a large enclosed trailer.

If I was not going to pull a trailer then a diesel pusher would be my choice for sure, motor in the back for sure. Just I would hate to only have 330 HP, that ain't sh!t after your used to 505HP.