ID 273 Commando that's apart

When I rebuilt my 273 2 bbl. in 1975 I added stock 4 bbl. pistons. I'm pretty sure the 2bbl. ones were flat on top. I know the 4 bbl. ones were domed with valve reliefs cut in them. The difference was pretty obvious. 66dartgt is right about the cam, you'll probably never be able to spot the difference. I put a "Street Hemi grind" cam in mine & had a lot of fun with it.