1968 Barracuda 383 Big Block torque boxes ?????

My advice is to not even question what Chrysler did. On a 68 you must have a fender tag to make sure the SO numbers match the body numbers. Having said that, never say never but MOST 4-speed cars had rear boxes and some had fronts. See them more often on Dodges than Plymouths. Most automatic cars had neither. I have literally seen 100's of 67 to 69 big block A-Body's in the last 40 years and that is one of the first thing I check.