Hard to start when stopped
I went down this road and did all the above.
I have a 30 over 360, .474 Mopar cam, Performer intake, tti headers, 750 HP carb, stock fuel pump, electric fan on front of rad thermo controlled , manual fan.
The one inch phenolic spacer did wonders but every so often I had the heat soak problem.
The overall best answer to my problem was a Griffin aluminum radiator!!!
The more efficient radiator dropped the temperature of the motor therefore dropped the temperature of the engine bay as a whole. I could even feel the difference while driving down the road. The whole car runs cooler now. I was amazed at the difference it made to the entire car in the hot summer heat.