I have them in my 69 383 also. Like he said, make sure ring end gap
is gapped correctly or you will break top ring. Also, if using the 906
heads which these are what those pistons were basically made for. Your
pistons are as close to "zero" deck as possible. Zero to get any kind of compression at all! Or even a few thousands above the deck wouldn't hurt at all. That's providing you are using the 906 open chamber heads.