There has been a lot of conflicting info on this subject. Mostly because of the restrictive exhaust manifolds. I think the 67"s were more restrictive than the 68's. Thats why most 68's are rated higher HP......
You are right. It was the driver's side they had problems with which is why in 67 they only got a half year of productions for the 383 Barracuda's.
Engineering changes in 68 bumped the HP up over 300.