Oil Pressure Sender for Aftermarket Gauge

[clockdoc]

I've replaced the idiot lights on my 1978 C10 (305 V8) with water temp., oil press., Voltmeter and tach, all 2 inch gauges. All are working except for the oil pressure, which I haven't found a place, that I can get to, to put the sender. Is there another port, other than the oil pres. switch port behind the distributor, that I can use? If not, any tips about getting to the oil press switch sender to replace it with the new one would be appreciated.

CLOCKDOC