definitive answer: plugs would have been factory for no heater, so there's no need for looping a hose
yes, you really should have a thermostat, the system was designed for one, for one thing it restricts the flow until the stat temp setting is reached, that is, it sets the minimum temp the engine operates at .... if you're constantly topping up the coolant you're likely filling it too much [common], it needs room for expansion, so cold leave it 1-2" down, a bit less when hot, but any time you fill it right up it'll spit some out when it gets up to temp
Bill
