Dang I'm racking up the posts on this thread....
I did just notice ANOTHER thing that Unit said though....
I thought that the "Mach 1" package was not offered until 1969?
Are you thinking the fastback GT? They made hardtop Gts also with the GT package.
I know the 428CJ was offered.....rated at 335 hp....0-60 in 5.9 (would have been way better without their crappy polyglas tires)...13.56@106.6....horsepower had to be 400....These hp ratings are all break horsepower though....not net like is used on new cars....
Steve McQueen used a '68 GT390 in the movie Bullitt. 4-spd.....mmm....sweet car.....