The most accurate I found is the WCCC one. All the auto parts store senders seem to read too hot:
I should probably clarify, my running hot problem isn’t a gauge accuracy issue. This car runs EFI with it’s own CTS sensor so I know the actual coolant temp. When stopped or moving under 25mph the temp starts creeping up. Start moving above 25mph and it cools right down. I have a new 24" ACP aluminum radiator, the 7-blade fan with correct shroud and new fan clutch (I’ve tried a couple from different vendors, no difference). In theory the rest of the cooling system should be more than adequate so I figured I’d give the high flow water pump a shot.