[walker]

I agree, clean it out, refill it with good coolant plus a bottle of that water wetter stuff. Check you belt tension. Put in a new t-stat. Also, check you timing, as I recall too much advance can cause higher temps. You may want to verify your guage reading as well, just use a meat thermometer in the coolant filler, and run it till it gets hot. Heck, since you have the cooling system down just install a new sending unit, they are only a few bucks.