Maybe I'm thinking of the '67 Camaro 6's that share the same firewall. I know at least one '67 f-body came with a cable so that's why the firewall has the indentation.
John, '67 Camaro L6 power plants use a cable (as do 68 & 69) I'm sure the indent is there due to the corporate cousins thing at least. The design of the Camaro And Firebird interior throttle arm for cable linkage is different, as would be the cables. For what it's worth...Cross-ram Equipped Z/28's use the L6 throttle design with a different cable...the throttle lever wasn't actually strong enough to deal with the double linkage from the 2 fours so there is a GM bulletin for a fix which involves shortening the arm and adding a gusset.
