Did Dodge ever offer rear disc brakes on their motorhome chassis? I can't remember, are the fronts disc? I am assuming this is a class A, or is it a class C? You would probably have to change everything from the master cylinder on down, since disc brakes require more pressure (no self energising action as on drums). Nothing wrong with a good set of drum brakes, I personally would just rebuild what you have.
On the engines; the 440 was probably one of the best engines Chrysler ever built, but the 413 was also a good strong engine. Nothing wrong with either one of them.
'97 Bounder, 32H, Chevy 454; ipd, Bilsteins, Air Lift, Banks, Hendersons, Solar.