Doug, thanks for the response re the coolant temperature sender/sensor. I plan to buy one soon. You'll know when you get the order. In the meantime, without draining the block to lower the water level, how much coolant will run out of the sensor hole when the piece is removed? Are there any surprises that I can look forward to if I approach the switch-out as mentioned?
Thanks in advance
Dee

Dee, we usually have the new unit in our hand, already has teflon tape on it, and slowly be ready as you unscrew the old one, stick the new one in. The engine can not,should not be too hot. If you are quick about it, do the swap. You might loose a touch but not much.

Dee, just thought I would inform you that Doug W's heating units come very well packaged and are the correct one for installation. Like Doug said, run your car for a bit, then let it cool down first. Prepare your new unit for installation...ie either put a sealant or some tape on the unit threads. Take the wire off of the old unit, then a little trick----before you unscrew the old unit out of the head, release the rad cap (only when it is safe to do so) and let some of the pressure out of the coolant system. Make sure that you have the new unit on the end of a socket wrench, or at least have a rubber glove on, because when you remove the old unit, you will get some hot coolant coming out of the hole. Then have your new unit handy and before you take out the old one, put the rad cap back on; this creates a vacuum that sucks the coolant back in! Then slowly unscrew the old unit and some coolant will start to come out. Off with the old, then quickly pop the new unit on. You should only lose a couple of spoon fulls of coolant this way. Connect your electric wire, and you are back on the road! ken