If you dry-shim to the top of the clearance ranges (0.007" Intake / 0.012" Exhaust), then do the final assembly with the O-ring in place, will the final clearance be affected by the presence of the O-ring? If so, by how much?
Anaerobic sealants typically have a 0.0005" (half a thousandth) film thickness. So dry-shim that much short of the top of the clearance spec (0.0065" Intake / 0.0115" Exhaust). Then when the sealant is added during final assembly, the end result should be clearances right at the top of the range.
For the old school Permatex Aviation Form-a-Gasket, the film thickness is 0.0015" (one and a half thousandths), so driy shim to 0.0055" Intake / 0.0105" Exhaust.
In horizontally opposed aircraft engines, the cylinder blocks are usually made up of left & right halves bolted together along the centerline of the crank main bearing bore. When they're bolted together with sealant, it's not uncommon to also lay a single strand silk thread around the joint. Similar to this O-ring layout, but just a thread laid in the sealant 'painted' onto the joint flange. But the thread affects how intimately the block halves make contact, and therefore affects the bearing clearances... so allowance is made when align boring the block.
So, is it necesssry to make any allowance for the O-ring material when shimming the valves? If so, how much?