Tailpipe for the 1968-72 vehicles will fit 64-67 & 73-77, but the tails will be short.  All 1973-77 3 ½” tails will probably need to be “dinged” a little between the upper control arm and Coil Spring—just like we have to do with headers sometimes.  On the 1973-up vehicles, tailpipes will have to be “dented-in” significantly between the upper control arm and the coil spring.