Not rare at all so value will be determined more than anything on condition. How much? Sorry to say almost certainly less than you're spending on it total. I know that's hard news. Unless it was a factory GT Equipment Group Option car and had A/C too, likely less than $20K. There were 21,683 J code coupes for the '68 model year. 2,847 of them were 3 speed manuals, about the same number as there were 4 speed manuals (2,851). The large majority were C-4 Automatics.