Super late reply. My 36 Chrysler Airstream has factory IFS. Sent from my iPhone using The H.A.M.B. mobile app
I think that axle was similar in appearance to the '33 Plymouth 'wiggly tube'. But the Plymouth's tube was dropped on the ends, and the 'drop' in the center curved forward. Now, the Chrysler tube (and presumably the Desoto and 'Airflow' design) had the same 'drops' on the ends, but the center dropped down, not forward.