oil pressure, gauges are usually connected to the engine block, generally to the access port over the oil filter or near the distributor base, depending on the application
Id suggest a new gauge and sending unit, if you don,t know the condition of the old stock parts, it generally requires a sending unit, and a connecting wire that connects the gauge to that sending unit, but naturally the pair must be a matched set
a few oil pressure gauges use two wire connections, many just a sensor and a single connection, most need a MATCHED pressure sending unit and a gauge
http://store.summitracing.com/partdetail.asp?part=ATM-2241
http://store.summitracing.com/partdetail.asp?part=ATM%2D5727&view=64&N=700+
theres a port for the sensor near the distrib and you could also install it near the oil filter in a few blocks
normally a 1/8" pipe thread
http://www.plumbingsupply.com/pipethreadsizing.html
theres also mechanical gauges available that require a tube for oil to reach the gauge, but they tend to be a P.I.T.A. and subject to leaks
