180 to 190 sounds about right, depending on what thermostat you have installed. Out here in the desert I run a 180 (82C). I think standard thermostats for the non-turbo 240s are 189 (87C) and 198 (92C). I definitely wouldn't use a 198 in a hot zone such as FL.

I wouldn't worry about 190-ish coolant temps, but 200 and over would get me concerned. Since your temp gauge in the cluster isn't working, you don't need to be concerned with a compensator board. I'm curious, though, as to where the sensor is that's hooked up to your accessory temp gauge. If it's in a vastly different location, you might be 20 degrees hotter (or cooler) than the stock location on the cylinder head.

10W40 oil is fine; 15W-40 won't be much different. If I wasn't using Mobil 1 10W-30 myself, I'd be looking for dino oil with a "40" in it.

When I changed out my original radiator a few years ago, for kicks I hosed out the core (externally) from front to back, and the volumen gunk that came out was just amazing. If you're at all concerned about your cooling system, for the cost of replacing lost coolant and about an hour's time I recommend pulling your rad and doing an external flush with a garden hose.
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Thank goodness we don't get all the government we pay for. -- Will Rogers