Overheating at idle

if it were me...
put a stock water pump and thermostat in your cooling system. A stock mopar water pump flows 20% more than a GM or Ford. The stock thermostat will keep your coolant in the rad longer.
Get rid of the clutch fan...they operate at about 80% speed at idle due to fluid slip.
Try a little more initial timing. Retarded will put the fire in the heads rather than the cylinders where the coolant will absorb the heat. A good test is to check and see if your headers glow in the dark.
If that all fails..just open the vault and get a griffin muscle car rad with 1 1/4" tubes. Then go find a red light and sit there without worry at an ambient temperature of 90 plus.