A couple of errors in your post. GN series 24994-25993 were not USRA design boxcars, as Todd Sullivan has pointed out, but "USRA clones" (how can clones be different?) with differences in the doors, door tracks, and most notably, the ends, which are 7/8 Murphy, not 5/5/5.
And the 27000-27799 series (famous for being the first Glacier Green cars) were rebuilt from 45000-52999 series boxcars, not USRA cars. The GN never rebuilt the USRA or USRA clones into steel boxcars. Examples from both series were rebuilt into stockcars in the 1950s, as the GN was retiring their older truss rod stock cars. Many others were sent to MOW service, lasting well into the BN era.