What kind of gauge are you using? How hot does it get if you use the correct(195°) thermostat? Has it boiled the coolant? Does it get hot at highway speeds, low speeds, or both?
Powerful and sought-after electric fans come from the Tauruses, '90s Lincolns, and '94+ Mustangs. I'm talking 4000-5000 cfm. There is a lot of info on them in the 5.0 forum. Spal also supposedly makes good fans if you feel like spending some money.