The best production figures I've seen are in the book "The Definitive Firebird & Trans Am Guide 1967-1969 by Rocky Rotella. From there you probably need to estimate. '68 Total 350 (excluding 350HO) engines 2bbl and 2 speed automatic - 49,879 (46% of all '68s) '68 Total V-8 convertibles (std & deluxe) - 14,544 of 88,618 total V8's (std & deluxe) = 16.4% So a SWAG would be about 16.4% x 49,879 = 8,180