On our 59 Caravanner (same platform as your Safari) with Air over water our city water hook up in under the street side front corner.
The way the system worked is you could fill the tank by the inlet on the curb side front. You could pressurize the system with about 60PSI of air. If your miserly with your water usage that was "supose" to last about 2 days. You could pressurize and fill by connecting to the city water connection. Water would back flow into the tank and pressurize at the same time. Problem is depending on the water pressure on the line filling, you might only get 20 gallons of water in before your couldn't overcome the built pressure in the tank.
This connection is also used as the tank drain. Not sure if this is original but a spigot is used as the valve and agender bender adaptor was made so you can hook the two male theaded connectos together.
On our unit the PO (My father-in-law) Tapped the the tank cap and installed a spigot. I can come up with two reason for this that seem plausable (PO not with us to ask). 1 so he didn't have to mess around under the unit to make the connection. 2. So that the tank could be bleed from the top to make sure the tank was full.
Now it sounds like your system did have the optional grover air pump. It's a 12v
pump that allows you to pressurize the tank. Should be located under the goucho/dinnete on the curbside front corner. On the front wall next to the window will be a light switch to allow you to turn off and on the pump. On our unit we have a pressure gage located next to that switch. I asume the gage is added as the instructions I have for the system indicate to check with a tire pressure gage on the fill neck shrader valve that was mentionined byt "The new kid".
Our unit is in the throws of restoration. I have not checked our Grover air pump to see if it functions.
I am undecided if I will retain this system for several reasons. Tank is a sealed unit so I can't verify if I have corrosion in the bottom of it. Big fear of that tank developing a leak and pumping 40 gallons of water out of a pinhole leak. My understanding is most of these tanks were galvanized steel and at 40 years old I question it's integirty if it is indeed galvanized steel.
I will probably convert to water on demand pump. I will proably also scrap the existing water tank and have a Stainless steel tank fabricated. Round tanks of the size used in our units do not seem to be available. Fabrication of a square tank would not be horibly expensive and guarantee fit in the current location with minimal modification. I will also be able to have a access plate on the top where I can visualy check the inside of the tank for any problems with contaminents and physically clean it.
Pros to the system is it's quiet, in the middle of the night it will function without a pump running and disturbing others.
Cons....40 gallons of water under pressure.