Temp reads high

Now that I have the 6.0 in my 1990 truck, the temps reads right at 260* on the factory gauges as soon as the engine is warm.
The temp sensor is mounted on the water pump.
I have a laser thermometer and when the gauge is reading this high the heads are only reading about 150-160* has anyone else had this problem? How do you correct it?

Mine did that when I had the wrong sending unit. Be sure to take your VIN to the dealership and have them order you the correct sender that is mounted in the cylinder head, not on the intake manifold.

Thanks for the tip. I'll get right on that.