Temp sender issue

['79squared]

So I have tried two temp senders http://www.oreillyauto.com/site/c/de...?keyword=wt359 and http://www.summitracing.com/parts/smp-ts76 and both are reading my temp at about 260 (pegged) when warmed up. I know my motor is not running this hot nor over heating. I dont want the sender to be in the intake (1/2"npt) so I am running the (3/8"npt) in the head. Aluminum heads with headers. Does anyone know which sender will not read so high? Or is there a way to maybe put in a resistor or something? I think the gauge is out of an '86 but I'm not 100% sure. The gauge is the one with the temp picture, not the word. If that makes any difference. Thanks and if I've left out something let me know.