You can check where is the coolant leak fairly easy. Put the car on the hoist (or jack stands). Remove the bottom engine covers. Use a coolant pressure tester (you can rent it at Autozone) and pressurize the radiator to about 16psi (when it is cold!).
Then just look for the leak. I doubt it is the head gasket as the Z32 head gasket is very strong. (unless you overheated the car). Hope this help!