So from what Bear says there were no rear side clearance lights on the sixties trucks like this
And the removable inspection panels in the front corners arrived in 75 like this - a little hard to see but there is a three ribbed panel with six machine screws
And the rear valence saw many changes. Early hinges (3) had vertical holes then 67-74 changed to horizontal holes then 75up to four hinges with wider horizontal hole pattern. Taillights also changed in width.
My inclination at this point is to make the clearance light a delete option. Customers could order with or without.
The inspection covers would also be a delete option.
I could really use a picture of the front corner inside the bed on a 65-67 truck. Mine has the covers - I assume the floor there just has four ribs like the rear corner????? Do the corner sections have the phillips drive bolts down through the x-members?
There rear valence has too many variables. I am inclined to make it blank and let the user cut what he needs.