A good buy IMHO. No emissions to worry about!

If you have the 50A version, you probably also have 2 air conditioners and with 5KW you can probably run both at the same time but doubtful if you can use the microwave with both on. Since the a/c compressors cycle on and off you might get by. Your converter is probably 55-60A at 12V so that would draw around 6-7a if the batteries are being charged. You can boost the ability to use 120V by shifting the refrigerator to propane and not using the 120V heater of the water heater but propane only. My last class A had a 5.5 KW Onan and it would pretty much carry everything but the electric water heater, at the same time. 

Looks like an interesting project and admire your dedication on re-purposing, looking forward to seeing your progress. Thanks for sharing.

Thanks everyone for all the info, it helps.   Steve - yes, I'll have to cut crossmember(s) at the hitch location. Might even need to open the bed completely to the rear but I'm hoping not to. I've got tentative plans either way. There's also some crossmembers missing in the pics that I had to remove because of the axle locations so I could get the bed temporarily mounted. (M1078 is single axle, my Freightliner as you can see is tandem). Had to travel over 1,000 miles to get the truck here. I was able to bring and borrow just enough tools to get the bed modified enough to fit and safely stay on the truck. I'll trim those crossmembers for tire clearance and relocate/reinstall them after I get the frame extensions and hitch done.

Apologies, Rod. I bumped it once, then lost track of it for you. I did see the latest video, but didn't put the two together. GLWS.