i would think at least for the front axle that a wider tire would be an improvement. the stock dual rear tires already have a fairly large footprint and can be aired down very low, assuming good tread i don't think there is much need for improvement there. the front will want to dig in a bit due to the weight on it. load is a factor here, i had an empty truck and the beach was no issue at all, the dunes seemed to be softer and the front did dig especially on the steep incline.
other factors to consider would be tire rim combo, tube/tubless, as well as bead-locks. if you are just tossing 395's on stock wheels with tubes than i think you'd do very well and you could adjust tire pressure according to conditions.
there are allot of sources but shipping is a killer so really you just need to balance cost with shipping and go from there. at least three popular choices exist for surplussed 395 tires and my personal goal is to get a hold of the mv-t tires as they have a tread pattern more suited to road use than the aggressive variants but if most of your use is off road than maybe something else would be better.