So what's the difference between the 1967 383 that made it less powerful than any other 383 Mopar from that year? Was it the exhaust manifolds?

Then, in '68, there were new cylinder heads - presumably the same as that on the RR. Same exhaust manifolds, though?

And, then, what did they do to the 383 in 1969 for it to reach 330 hp? And I presume it still was a different 383 from the 383/330 that was available on non-performance B-bodies (and AC-equipped RRs)?