69 M code A body question

69CoronetRT said

What was the difference between the 440 exhaust manifolds and the 383?

Here's the heart of the question...

Weren't the 440 cars rated at 375 horse the same as the B body 440HP?
If the A body 383 was de-rated due to restrictive exhaust manifolds, why did Chrysler not use the 440 manifolds, which do not appear to be restrictive, on the 383 cars?

thanks

Click to expand...

Both the 383 and 440 manifolds bend around the steering column somewhat like the small block manifolds do but because the 440's block is taller that bend needed to be relocated although I have seen 383 manifolds on 440's in a-bodies and they seem to fit. Also the drivers side manifold changed from '67 - '69 so Mopar gave them different HP ratings for each year but I'd have to go back and look to see what that rating was.