Question 1965 vs 1967

The exhaust manifolds changed in 1967 with the wider engine compartment. The "Y" pipe is different but the same ID. The resonator and replacement mufflers were the same for all three years. Not sure about the pipes. The resonator is straight thru. The mufflers can be either straight thru or normal muffler for 66. By 67 they were a normal high flow muffler. "Straight thru" sounds the best in my opinion.