John - Your seat does look to be original, but the pictures make it look like perhaps it's has been previously recovered with extra seat padding added. It looks like added padding was laid across the top and wrapped over the sides which is likely the cause of the side "bulging". Also could be that the side support spring rows on either side are sagging as they get the most use when getting in and out of the truck.
Below is a screenshot from a 1941 Chevrolet Truck Advertisement (same as your '46 for seat specs/dimensions) that shows the sides of the lower seat pretty much straight up and down, which would leave them away from the door panels.
Honestly, if your doors are going back as-is with the wear marks, if the seat is currently comfortable and supportive I'd leave it be.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
