Did a crate engine switch from original 350 to a ZZ4HO. Temp guage never went over 110 on old engine or new. Put in a new guage(roger's) and no change, so just installed a new correct temp sensor for a 1974 vette and guage goes to 230-235 and stays. Borrowed a pyrometer, checked radiator, housing and lines  all measure 175. Haven't had any overheating symptoms so assume guage is not giving a correct reading. Anyone have knowledge of what may be going on?

The sending unit is out of calibration with the gauge.  One of the two needs changed.  The sending unit is a lot easier.