Then late 1947 through 1949 Chevy/GMC trucks had a very different wiring harness than later 1950 through 1955 years (actually, will not interchange with any other years).

Its difference is seen just by raising the hood. On the firewall lower side of the voltage regulator is a vertical row of five fuses protected by a removable metal cover. Actually, when you order a new replacement harness, you will quickly see this is two harnesses that will be joined together by the five fuses. This justifies its higher retail price.

It’s Advantage:

Each fuse protects one part of the truck’s electrical system. When seeing the blown fuse, the truck owner can quickly locate an electrical short in the system. When seeing the blown fuse, the truck owner can quickly locate an electrical short in the system, sometimes with the help of the owner’s manual.

In 1950 and newer, the wiring is condensed to have two fuses!

The firewall with fuse box on right side.
As you see it.   
The cover removed.  

Cover as you see it.
Back side of cover with the clip to hold two spare fuses.