[hbens]

My thoughts: Keep the engine and running gear running like the Swiss Watch. Change it out if needed or an opportunity comes along you just can't pass up. I'd stick with the same fuel but upgrade engine and tranny if opportunity or need arises.
On the inside I'd update to a residential fridge if possible. Keep the old paneling which brings back that era. Maybe though, updating to the newest and best as you can would be a great surprise. Imagine the outside restored to look like it did when it rolled out of the manufacturing line and when you walk through the door you see Newell 50 years newer!