On temperature, I have an original guage, and a reproduction sender to match the original. Note: not a substitution gauge, a reproduction gauge with the same resistance curve as the original. American Autowire did it for the Corvette restorers, whose gauges read in degrees. It drove them nuts not to have them read right. It turns out they use the same resistance sender as squares up through (I think) 79.
The full details on senders are in this thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=630399
My gauge now reads just shy of straight up when everything is operating normally.