You can leave the thermostat housing in place but the distributor must be removed. There's an adapter shaft that seats in the head that runs down to the oil pump. It has to be removed to facilitate the removal of the head (it just slides out). The shaft has a slot cut in it's top, note it's position as it's cut off center to aid in getting the distributor set back into it's proper location at reassembly. It wouldn't hurt to remove the cap before you pull the distributor and noting the position of the rotor.
Also, don't forget to remove the coil and temp sending unit wires!