Before you go looking for the 6-cylinder throttle "cable" ...
The '67 OHC Firebird uses a rod that is shaped differently than the V-8 rod. The firewall has the formed features for the cale that was eventually adopted for '68, but I'm reasonably sure that none of the '67 OHC Firbirds used a cable.
The '66 and '67 Tempest use throttle cables for the OHC.
But I am sure that all their blocks only have two bolt holes on each side.