Temp sender

[Rockettvr]

Anyone know what sort of resistances this should put out at various temperatures ? Last year my temp gauge on my 350 always read quite low ( around 80 deg C) changed the stat for a new 88 deg one thinking it may be stuck or faulty but gauge is reading even lower struggling to get to 70 even after a bit of spirited driving. Guessing it's the sender on its way out as water pipes feel much hotter than the 65 deg indicated. Any one got a part no for a replacement please as there seems to be a few different types
Cheers fellas
Ron