I believe I posted in the wrong section before! Sorry, new to site.

I have a 1960 F100 that someone transplanted with a 1957 312 Yblock. The truck has an aftermarket gauge set and the standard dash gauges/idiot lights.
My problem is in the temp gauges. The aftermarket gauge reads a safe temp + - 180. The location of the sensor for the aftermarket is near the #8 cylinder intake. The dash gauge pegs the hot line in about 10 to 15 minutes of drive time. That sensor is located on driver side block just above oil sending unit.
I have used an infrared temp probe (laser) and get basically the same readings as the gauges, respectively.
Could I be reading oil temp on the dash gauge or do I have a water flow restriction in the lower part of the motor?

 

I think the location of the dash gauge sender is where a petcock is usually installed to drain the block coolant on driver side. So it would read water temp.

 

Normal location is in head, behind intake by #8 (driver's side, or -left- at top rear of motor assembly). There is an oil pressure gauge location on side of block near oil filter location. Oil temp could easily climb above water temp. Perhaps you could pull stock sensor and see if water or oil comes out?

Got picture? That may help.