AFAIK, the current thinking is that all the WP reefers had Built-Up underframes.  I do not know of, and have not heard even rumors of, any photo of a WP reefer with a Bettendorf underframe.

My recollection is that some of the Car Cards for the WP reefers were marked R-30-12 (crossed out) which would indicate a Bettendorf underframe.  But my theory is that PFE just had a pile of those pre-marked Car Cards sitting around when the WP reefer Car Cards were initiated, and some of those cards were used for the WP cars.  That could easily be the source of the idea that some WP reefers had Bettendorf underframes.  The Car Card itself does not specify the type of underframe.  

It's been ages since I looked at WP reefer Car Cards at CSRM, and there aren't many.  One sure fire way to test that theory would be to find a photo of a car for which we have a Car Card indicating a Bettendorf underframe.

But again, I know of no photo of a WP reefer with a Bettendorf underframe.
If anyone has one, please share it.

The WP reefers were not included in the PFE Freight Car Diagrams (which list underframe), presumably because PFE did not own the cars.
https://harley-trains.smugmug.com/PFE-FRT-DATA/PFE-1951-Diagram-Book/
Don't know if anyone has a WP diagram for those cars that might shed some light.


Hope that helps,
Dick Harley
Laguna Beach,  CA