as far as brakes go, Grigg did mention, "Then if you desire different brakes or axle gears swap rear axle entirely and parts of the front axle to get newer brakes.". He has done some pretty extensive writeups on swapping out pieces on the front end for newer stuff while retaining the original axle itself. You can always go look at some similar size motorhome or stepvan chassis and start measuring for overall width and go from there but, it is entirely up to you which way you want to go and how much old vs new to use on it!
