1967 B body 383's only had 2.25 exhaust pipes, and I think the tailpipes were only 1 7/8" (but I could be wrong on that, might have been 2").

Plus the 67 B body 383's didn't have hi-po exhaust manifolds; they had the ones below, under my 69 A body manifolds. No way the A body manifolds cost 45 hp.

One more thing: Because the 67 driver's side manifold is different than the 68-9, and the 67's hp rating was the lowest, everyone assumes the 67 driver's side manifold is more restrictive than the 68-9. I've seen both, and I don't see the 67 being more restrictive. The 68 A body 383's got better heads, intake manifold and carb, and the 69 got a better cam; that's where the increased hp ratings in 68-9 came from. IMHO.

OK, still one more thing: A 2-barrel 383 with a dinky 252 degree cam and single exhaust was rated at 305 hp in 1964. There's no way it really had more hp than a 67 A body 383 4-barrel with dual exhausts. I don't know why Chrysler dropped the hp rating for A body 383's compared to B body 383's, but I think it's pretty obvious they did.