Nice lights!
If you pick up your power from the back of the ammeter, it will show discharge when they are on, just like the headlights, I like that. Put an inline fuse in this wire, and attatch it to the hot side of your switch. If you have an original switch, it may incorporate a fuse already. From the switched side of the switch, run the wire out to the lights, and spilt the lead, to power both lights. The lights will be grounded by the connection to the bumper bracket, so make sure they have good paint free contact there. That's how I did it on my '50.
Here's the factory info from '51. They have a place for a jumper wire running to the tail light terminal on the head light switch. I suppose that's so when its foggy, you only have to turn on the fog lights, and the tail lights come on automatically, that way you don't have to remember to turn on the park lights.
http://chevy.oldcarmanualproject.com/accessories/1951am/51aim48.htm
