For reference I bought this harness (https://brillman.com/product/john-deere-serial-583999-complete-wire-harness-1-wire-alternator/) and this light switch per their suggestion (https://brillman.com/product/2-position-pushpull-switch-3-8-32-mounting-threads/).
Both the harness and light switch are correct for your tractor.
The tractor has been converted to 12V negative ground with a one wire alternator.
My other concerns are the hookups to the amp meter.
Take a look at the photo below of the ammeter on Easy our 46 slant dash Model A.
Note the wire from the starter switch is connected to the POSITIVE post on the ammeter.
Note the wire to the one wire alternator is connected to the NEGATIVE post on the ammeter.
I also have a spare wire (#40) from the kit that's just labeled as "light switch" but I don't know what it connects the light switch to
Take a look at the photo below of the light switch on Easy our 46 slant dash Model A.
Note the wire to the ammeter is connected to the POSITIVE post on the ammeter.
Hope this helps.