Early A, 273, 340 manfolds dual exhaust.

The early LA manifold on left side had about 90 degree turn at the bottom of it. One owner compared the restriction to pooping through a straw LOL. At the same time, a heat riser in the right manifold would close pushing more exhaust pressure to that left side, yet it seemed to work, good enough for a stock engine anyway. That 90 degree turn in the left casting disappeared for 66 or 7 but even the 67 commando exhaust was still a single pipe. From what I've read, only the Y pipe was a little different from standard 273 2 brl.
I think I would want a later left manifold without that kink even if not 340. The value of a good set of 340 manifolds is about half of that 800 dollar dual exhaust system. All just points to ponder. Good luck