The exterior skin looks pretty good there, so you have something to build on. Of course, the interior looks as one would expected for having the interior demolished.
You'll very likely need a new furnace and water heater, they rot out with age. The refer (fridge) will probably need a new "cooling unit" unless it has already been done. If the refer is in good cosmetic condition, it is worth keeping and getting the new cooling unit as a replecement will make it work like a new one.
On my '74 Sovereign
there is a small plate to the right of the dor latch that has the complete serial number.
Another good item to consider replacing (if it hasn't already been) is the 120VAC to 12VDC converter. The original one boils the battery in fairly short order if you just leave it on. New ones now have a three-stage circuitry that maintains the right AC voltage to the battery to keep it in good condition.
Please be sure to post pictures as you go ahead with the interior replacement? We are hooked on watching others do that work