65 barracuda exhaust

I would suspect the aftermarket pipe sets are cut and bent for the longer wheelbase and can be shortened as needed. As others have mentioned, the earlier cars have a slightly narrower engine compartment, but the engines themselves are the same width. 67-up exhaust will bolt right up to 67-up manifolds. The narrower engine bay comes into play because the steering column is about an inch closer to the manifolds in the earlier cars, and may cause interference issues especially with power steering. The trans crossmember either needs to be modified for clearance or the right side pipe will have to ride a bit lower than the left. Later cars had a more centered gas tank which made duals an easier fit so avoid 70-later systems. The main reason 64-66 systems are different is the fact that they had an oddball left side manifold outlet and were never dual from the factory.