I agree, if your engine fan isn't kicking on until 230 or 240 then it's bad or the wrong one! Verify the temps, maybe it's not the heavy duty one for RV's. I'd also do a cooling system flush, there may be build up in the engine block if it wasn't flushed during the radiator replacement from years ago. I'm in Avondale, so not too far from you, and after I did my coolant flush I did a 70/30 distilled water to coolant ratio. We don't have to worry about freezing temperatures in the valley, and more water is better for removing heat! BTW, you didn't adjust the carburetor on a `97, Ford went to fuel injection on the 460 in `88:)
Let us know what you find!