jdl,

All Advance-Design (note: not Advanced) trucks had a fuse box. Here is a discussion about Advance-Design fuse boxes. In that discussion is a link to the 48-51 Shop Manual section that describes the fuse boxes (and the change-over in 1950).

It looks like a fuse box (actually, an accessory junction-block) became an option in 1955 second-series trucks. If you read on in that 1955-2nd Truck Shop Manual, you'll find the discussion about a circuit breaker being part of the light switch, providing protection for the entire stock lighting system.

Tim