seat exchange
you should be able to use up to 66 cause the 67 models trucks had a larger seat so you are knid of linmited in that regard if you want the stock look if not you might be able to use up to 77 model with slight mod's but I am positive they switched sizes in 67 cause that was a selling point in 67 larger and widrr cab space i belive it is something like 1 3/4 inches difference there hope that helps out some.James