Tim,

The only PFE 40-ft steel reefers that I know Sunshine did were the R-40-10 and the R-40-26.

The R-40-14 and R-40-20 are very similar, with the -20 being 1-1/2 inches taller.
I would make an R-40-20 from an InterMountain R-40-10 (and ignore the taller height), but I suppose you could replace the roof and underframe of a Trix car and narrow the ends.
See: https://harley-trains.smugmug.com/PFEModels/PFE-Steel-Ice-Reefer-Models/R-40-14/
and  https://harley-trains.smugmug.com/PFEModels/PFE-Steel-Ice-Reefer-Models/R-40-20/


Cheers,
Dick Harley
Laguna Beach,  CA