Yeah, 4 speeds were used in trucks in '68. So were 3 speeds. Take a look at the SPID sticker on the inside of the glovebox door. Sometimes it shows the tranny in the list if it was an optional thing. Also, take a look at the floor. If it's stock the hole for the shifter will be pretty clean and straight. Is it possible that it was changed? Yeah, but most likely not since the majority of people will go to automatics instead of the other way around.
