I don't like KB pistons, valve reliefs are huge and the dome impedes flame travel. You'll be lucky to have 9.5 with 906's and a thin steel shim gasket.

Has the block been sonic checked ? .060 is touchy on a 383.

The heads are still an issue unless you got them FREE, they are ported by someone that knew what they were doing and they are already rebuilt, otherwise any money you put into them is wasted money.