I agree your truck can handle any of the Montanas. Our 3295RK is heavier than the 3650RK's GVWR and we've very successfully towed it over mountains, including the Rockies, with a '99 F350 V10 gas, then an '03 F350 with the 6.0 diesel, and now tow it with an '05 F250 6.0 powerstroke diesel. The biggest problem you'll have in my opinion is your smile muscles getting tired.
I think you'll find the Montanas tow beautifully, at least our two Montanas have. No white knuckles here, even in heavy winds, even being passed or passing 18-wheelers.