On my 1954 (different gauge) the reducer goes on the "input" side of the gauge, the post behind "Empty").

If it is installed reversed, the gauge gets fried. Originally, there was a red warning tag on the Full/Sender post on the back of the gauge.

Here is a photo of the runtz-style reducer on a pre-54 fuel gauge. You can see the remainder of the red warning tag on the sender side/post.