Sorry , the tailpipes are one size fits all , they only list 3 tailpipes ,63-66 , 67-69 barracuda and 67-76 A body
here is a pic of a 71 duster with 2.5" pipes , the same pipes I got and they are NOT correct for a 67-69 dart , hell a 67 A body only had a single tailpipe even with a dual exhaust .