I've never had any experience with aftermarket aluminum heads (yet), but it has been my experience that it doesn't take much to warp aluminum heads. Are you still running the original radiator? If so you may want to look into buying a new one and a new high flow water pump. For the time being I would pull the thermostat back out.
Keep a very close eye on your coolant and oil over the next few days for signs of a milky brown substance. You may want to invest in a compression checker and do a check on each cylinder just to be safe. They should all run within 10% of each other. Mine run from 140lb to 150lb. It's not a guarantee if everything looks OK, but it's a start.
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