... And, the factory a-body 383, and particularly the 440 version are INSANELY expensive..... because they flow like crap and were frequently replaced with headers and thrown away...
There were only 7,926 Darts and Barracudas with a 383 made from 1967-1969. That might have something to do with those manifolds being rare. Most of us knew not to dump them for junk headers.