Yes I have em cut 60 thou. ideally you'd want to mockup the heads back on the block & see how much if any the intake faces of the heads need to be milled to get bolt hole alignment in the ballpark (your port alignment is what you are really after) & that means another trip to & from the machinist or you can have the intake milled which is another trip also which might make the intake only fit your eng with the milling but if it'll be together for years then no big deal. there may be a preload (pushrod length) issue to be dealt with, maybe not, you'll see when you mockup. I milled some 906's 60 thou and advanced the 509 cam 4 deg & it woke it up. agreed SCR is the issue but if the short block is in the car & you dont want to pull it & go thru it (I totally understand that) then yes go to town on the heads & dial in the cam then dial in the ign curve