How far are you going? I see you have a roof ac unit, do you have any roof leaks or does the roof seem to sag any? I'm getting ready to gut my '72 and I haven't decided if I'm going to leave the roof unit or put a vent back and put a window unit on the back.
I'm just getting it usable for now, had to re-do all the plumbing, build a closet- someone had tore most of it out, put in a new toilet, and maybe a new floor covering for the wife! I have the leaks fixed and will begin to replace the front-top and rear-top paneling in the future. No leaks or sagging around the ac unit. Had a leak around the vent over the stove, but replaced that.
Re-placed water heater with outdoor tankless, these are my city, cold out and hot in. Also installed a plastic water tank.
I also had to replace all of the plumbing in mine. I used CPVC and lots of valves so I could isolate anything and everything. Just this summer I got a roof leak that I haven't been able to find yet but being 40 years old, I figure it's time to update all the way around and change the floor plan while I'm at it so I'm going to gut mine and start pretty much from scratch. I think I'll leave my dinette and drop down bunk in the same place and the toilet will stay put but I'll relocate the couch/bed and have all new cabinets, floor/wall/ceiling coverings. While it's gutted I'll look for cracked welds and/or rusted framework as well as the source of the roof leaks.
I really like this setup and may copy it. I don't have a water heater in mine right now but if I put a real shower in I will have to - let me know how you like your instant unit. I already pulled my fresh water tank as I'm really not a fan of those - they get nasty in my opinion. and mine doesn't have a gray tank anyway so I'll just go places where I can get a full hookup.
Thanks for posting the restoration pictures. You might want to consider replacing the rusty exterior screws with stainless steel ones. Our stink pipes are covered with cloth. You could sew one and put it together with velcro sewed on the material. Mine tended to slip down so I used some soft velcro ties I found at my RV store. I could also see ties made up with fabric or a pretty ribbon in a bow tie. Keep up the good work. When I did my restoration on my 1990 I gutted the upper walls and used 3M bondo on the inside to seal my pinpoint holes in the fiberglass. This could also be used on aluminum. Lexell caulk is excellent to use on interior and exterior. Best of luck as you continue to restore. Keep us posted.
One more item as you restore. Remove all your windows are reseal with Butyl tape and Lexell caulk. I recently posted how to do this.