Through 1968, the OHC had an air cooled 2-speed transmission behind it. Not until 1969 was a TH350 used, and not all auto-equipped OHC's had TH350s in 1969.
An air-cooled tranny does not need a cooling circuit on the radiator, so Pontiac used the same part number for both manual and automatic applications.
Edit note: There were also radiator cooled automatics installed behind OHC's in '68
Last edited by P. M. I. USA; 10/31/0805:07 PM. Reason: More Research
