What level of noise constitutes "noisy" does vary somewhat from person to person. A front engine motorhome (gas or diesel) will almost always be noisier when traveling than a rear engine motorhome (gas or diesel), and naturally the volume of the noise is greater when under a larger load such as when climbing a hill. The Ford V10, in particular, revs quite high for a truck engine under load, and so produces relatively intrusive and noticeable noise.
There are variations in how well isolated (or perhaps how poorly isolated) the engine noise is from the interior. It's certainly not beyond the realm of possibility to carry on a conversation in a gasser while driving. I'd suggest going for a test drive or ride in a few different units to get a general idea of the noise levels.