What fan is on your car now?    If it is the standard 4 blade the seven blade clutch fan will make a big difference. Not just the number of blades but the pitch as well.

Carl. You should see a difference with the clutch fan over the four or five blade fan. (If you PM me I can tell you how to tell which one you have LOL).
 Make sure that the clutch is good so it will freewheel when the RPM's are up. Are you running a fan shroud on the car? A shrould will guarantee that the fan is pulling is coming through the fan. Stay with the lower Tstat. You want the water to stay in the rad long enough to be cooled by the air.
 Let me know how you make out. I have a 7 blade flex fan I took off a 69 GMC with a 396 and AC which kept that motor cool. I don't want to sell it right now but you can borrow it to try it out.

I don't always trust an electric gauge to be as accurate as a mechanical gauge. Todd had a good idea to check it with a digital thermometer. I have one in my truck all the time if you want me to stop by the next time I am over at Stan's and check it just let me know.
 I know what you mean they can be a pain. The car that is. It's probably being stubborn after sitting for so long. You just have to get it out on the road where it want's to be. That big block probably feels like a caged animal.
 Let me know if you need any help.
 Brad