Fill my Coolant reservoir next day no coolant

Are you driving the car in between these coolant top-offs? If it's not leaking and pooling on the ground under the car, then it is leaking out while driving or going out the tailpipe. There is an overflow tube coming radiator (or degas bottle if your 87 has one). If system gets over-pressurized while driving then it will flow out from there to the ground. There is also a drain tube from the heater core box to the ground, if your heater core leaks, then it may only leak when engine is running and then draining to ground via drain tube. (if that tube gets blocked, then you would have coolant leaking into interior from heater box.) Finally, if you have a bad head or intake gasket you may be losing coolant out the tailpipe. Not all blown gaskets result in oil-contamination. You may also want to check the water jacket of the engine, mainly the freeze plugs, as water only moves through the jacket when engine is running, look for leaks then. Can also try a pressure test on cooling system, that may reveal a leak not visible normally.