Gas,
Can you post a picture of your unit. Show the inside and tilt the tank back.
The piston would move with the lever and allow the syrup to flow.
I think I was confusing it with a Dole Super or a Dole Deluxe. This unit could possibly not have a float as it's one of the earlier fountains.
The carbonator could have been remotely located anywhere, back room, basement, under the counter. There should be a drain somewhere in the ice bin, look below for a pipe coming out the bottom. The carb line would have been connected via a threaded fitting on the bottom.
Did you buy the one that was recently on e-bay?
You can try here for a repo manual,
http://americansodafountain.com/id4.html