WC-54 - Restoration

[HQ-88]

I am in the process of restoring a WC-54. On the passenger side of the vehicle there is a strip of wood, about 4ft by 3in. mounted above the rear wheel forward. I have looked at multiple photos of completed WC-54 and in only one do I see this wood strip. Can anyone tell me what this is for, and why some models have them and others do not?

 

[Superdave]

For the pioneer tool rack