CJ running hot!
trw
Jeeper
I think you may need a ground strap from your engine to the frame and tub. Or at least clean all of your battery cable conections.
You could be "burning" your coolant by not having a good ground. Most of the times I've seen the coolant turn brown it's been a electrical issue.
Once the coolant is burned it will not transfer heat very good and it will also freeze at a much higher temp.
I do recommend a 180 t-stat, that's what I run in my AMC 304 with no problems.
well the coolant itself isn't brown, it just has a lot of dirt/rust in it, that settles to the bottom of the upper water tank, you can see a layer of at the bottom once it all settles, but the coolant is still bright neon green, but it does get cloudy while the engine is running.