Leave the thermostat housing top off and fill the cooling system through that hole until the coolant is almost level with the top of the head casting, then install the thermostat and finish filling the radiator. It's the simplest way to avoid an air lock caused by a closed thermostat.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!