There are actually two (slightly) different flareside boxes for this 67-79 time frame. The first style was the '53-'72 style. From '73-'75, Ford didn't offer the short version but still sold the 8' box. The 6.5' flareside box reintroduced in '76 used shortened (lengthwise) sides from the 8' box. It was wider than the early box to match the wider rear axle introduced in '73 and had inner wheel bulges on the sides. In '77, Ford flattened the top of the box sides and this box was used with the round fenders til '79 and then with the squared off fenders until
'86.


mike