OIL PRESSURE

I have a 1971 vw beetle that is modified with a 1776cc motor with external oil cooler and with vdo gauges that tell oil pressure and temp. When I start the car the oil pressure gauge shoots right up past the 80 psi mark and maxes all the way out, and never changes. Also the oil temp. Never changes that gauge doesn't move it sits all the way down by the 120 degree mark. Can you tell me what you might think the cause of this is. Is it the oil pressure switch and if it is how and where does the temp gauge reading come from.