I was looking at my old Mopar Performance Parts Big Block B/RB engine book P/N P4876825
And in there it states that the 1968 and 1969 383 engines(4Bbl) have positive deck height.

I know that just because its in the book, does not make it true, but just thought I would throw that out there.
They were also saying with stock pistons(with NO valve pockets) that you should stay away from camshaft duration larger then 285 degrees, and high lift cams, they do not go on to give a number of what you are safe to use.