a picture is worth a thousand words

Here is a picture of Tyler Neff's 9N. On the left is the ammeter. The guage on the right is the Oil pressure. I imagine you figured that much out. On the right is the choke knob directly beneath the O.P. gauge. At about the same level on the left is the light switch. Now on tyler's tractor, he also has an ignition light which is located directly below the ammeter in this picture. The lightswitch knob is closer to the steering column on his dash. I don't remember where I installed my light switch (directly under the gauge or slightly closer to the steering column) but this is the general layout of the dash. Do some research on your tractor to figure out whether or not it had the extra ignition light as that was dropped at some point. According to the Originality guide, the light was dropped in 1941 but was used in '39 and '40.

Hope this helps!

Jeb