Alan---The stock head thickness for the 8.5:1 head is said to be 3.460.
There should be enough adjustment in your ball studs using the proper
jam nuts, unless as you suspect, that the had has been milled to a
higher CR. You might be able to pick up a machined surface on the block
from which to get a measurement, say down near where the water pump is
bolted on. (This would be tricky, at best)
Should you find that you are out of threads because of a head milling,
shorter pushrods would be the best way to go in keeping the right wipe
at the valve stems. A less accurate way to do this would be to equally
shim up the rocker pedestals, remembering to keep the oil delivery hole
open at this pedestal.
Dick
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