I was unable to edit the above post so add the following here.
The issue of sticking valves: This would be a suspect if you installed a rebuilt head with new valves and new valve guides and if the machine shop neglected to provide the correct clearances.
With regard to the changes to the head that you are considering, you might peruse this manual as it may provide some clues. Start off by measuring the volume of your combustion chambers so that you can calculate your compression ratio.
Cheers!
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