First 1967 383 installed in a Barracuda
As far as pre-production, somewhere I have a blurb in an old (1966) magazine about a '66 Valiant test mule with a 383. At various times there were problems with production parts. One of the weirdest was the run of 1968 Valiants with Barracuda dashes because they didn't have the Valiant parts available (Tech bulletin)