The drop center Eaton H052/72 was used by GM (Chevy more than GMC) until 1972 in the C and K ,20 and 30 series, in the 10/15 half tons there where used until 1966. Hope this helps broaden the search pattern.
~Boone 1932 Confederate 5 window Sport Coupe 1936 Chevy 1/2 ton pickup 1953 Indian Chief 1947 Indian Chief 1946 Indian Chief
