With 906 heads you would need a "quench pad piston" with a pad that extends up into the head cavity. The pad and/or chamber is machined to get quench clearance (.035-.040"). Only trouble is KB who makes quench pad pistons doesn't seem to make one for the 383. It would likley have to be a custom piston.

The Edelbrock's at $745 each (assembled, Mancini) may not look so bad if you can find a shelf stock flat top piston that gets you zero deck.