1976 Nissan 280Z erratic gauges

Water Temp/Oil Pressure Gauge: Three months ago Temp gauge started ranging from zero to 170+ during extended freeway driving. Two weeks ago, the oil pressure gauge became erratic with reading from zero to 1/4 and normal 1/2 marks.
Amp/Fuel Gauge: Amp has registered near 15V zone for past 30 years. For past 2 years, the fuel gauge has randed from zero to 3/4 after fill-up.
Clock: Stopped working about 2 years ago (power to clock, but inoperative).
Local mechanic statement: Gauges have built-in regulators which are bad on the fuel & temp gauges, and inconsistent on the oil gauge. Vehicle needs 3 replacement gauges plus oil pressure sending unit.
Question: (1) With symptoms described, are there any other possible problem areas or parts that would cause the erratic behavior? (2) Any recommendations, sources, or advice to repair/replace gauges, (3) Can the car be driven with current gauge problems with fear of damage or breakdown?