Oil pressure idiot light stays on

All throughout the break-in period and tuning on an indoor dyno, the 360 we built for my son's car maintained a solid 60-70 lbs oil pressure. Engine is now in the car and running great; however, the dash light stays constantly on. Any ideas why this is happening? I suppose I could tie-in a pressure gauge and see for sure what it is, but I am wary of a small tube bringing hot oil into the cabin area. Anyone using an electric gauge they would recommend?