[Jembow]

I've had this truck since 1979 and have just started to sort out the rust. In Mack Hils 1979 book he shows a photo of a wood bearer under the bed, and the vendors offer this, but I couldn't see it on my truck. The repro side rails I bought didn't fit and then the light bulb came on! My truck has the body sub-frame of a passenger car running under the bed.

Is this on all E28 pickups? Mine is May 28