The earlier years ran the door relays in the channel

If you have a door relay for a 47 or 48 ? you can mount them the way you described.

The 50 mounts the way I have pictured.

http://chevy.oldcarmanualproject.com/booklets/4748sctc/4748sctc11.html
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0109.htm

You might have to push your Handel to open the door.