Assuming the new heads have the same combustion chamber volume. The early intake close of the 255 cam, will already have your cranking compression and corrected compression in the higher range. Adding even more compression via pistons is going to exaggerate that even more. Hopefully they give it a really good tune, so it doesn't ping. You'll definitely be needing the ACR's. if the new heads have more chamber volume, and the new pistons are there to make up the difference, then forget what I said!
2009 Vivid Black FLTR/120R/Dewey's headwork/TMan 625G/Fuel Moto XXX 2/1/2 w/4" mufflers/HPI 55