I have a 69 383 4Bbl A/C(turquoise, duel exhaust Holley carb)I just had the heads off because of a stuck valve. So I removed the 906's heads and cleaned up top of block for my re-man 1971(346)heads and my pistons are flat top and if they are not positive deck height, then they are so close to positive and you would need measuring equipment to tell the diff, because with my finger and eye, it looks to be above the deck(very small amount)
I do have photos, And the driver head is not torqued down yet, so I could take it off to measure I DO NOT want to but I could.