I am now pretty set on getting a TH350 to replace this one, but...
From Wikipedia (I know, not the best source): "From 1967 to 1969, the Super Turbine 300 was also available on the sporty Pontiac Firebird with the overhead cam in-line six-cylinder (230 and 250 cubic inches) or small V8 engines (326 and 350 cubic inches)" But, there were no sources/references cited.
Lloyd www.firebird67.com 67 Firebird 326 Coupe. Currently undergoing restoration.