I've got a 310 with an IsuzuTurbo Diesel and I get low 11's when I tow the toad and high 11's the rest of the time.
I've been told by most of the diesel mechanics I've talked with that the engine will out last the MH IF you respect the temperature limit of the turbo charger. I limit myself to 900 degrees even though the actual limit is 1100 degrees. Also they've stressed the importance of oil changes ever 3000 miles.
I feel comfortable with the engine but I will admit a little more power would be nice. I've never had her in the mountains but I'd guess she'd be a little under powered.
I don't know what the rear end ratio is but I'll do a little digging and find out.
Happy trails 2 U! Stuart