Okay, first assumption that has been made all along is that your 22" radiator is in good condition. All the tubes are intact, there is no build up or electrolysis happening inside the unit to restrict flow. Is that true? Also, are you running an automatic trans and using the stock in radiator cooler? This can add substantial unintended heat to the system.
Here is an experiement that will only cost you time and a thermostat gasket.
Remove the thermostat and drive over your normal route/routine. If the heat condition gets worse, then the coolant is going through your system to rapidly. If the heat stays the same then you need to speed up the coolant flow.
If you need to slow down the coolant, replace the thermostat with a restrictor, which is a flat piece of metal with a hole in it. The hole size can be changed until you reach the right amount of coolant flow. Start with 1/2".
If you need to speed up the coolant, then drill a few 1/8" holes into the thermostat plate to allow coolant to continue to flow during the warming process or leave the thermostat out altogether.
The other option is to overdrive or underdrive the water pump pulley. A bigger pump pulley drives it slower, a smaller pulley drives it faster. You also can add a plate to the back of the water pump impeller to aid in the efficiency of the impellers ability to move coolant.
I also believe you need to have the pressure on the radiator cap checked out as well. A weak spring in the cap will not allow the coolant to absorb as much heat as a good cap. Every pound of pressure in a cap raises the boiling point 2 degrees. So a 20# cap raises the boiling point from 212f to 252f. That means the coolant can absorb and disapate more heat before it turns to vapor than it can with a weak cap.
