Mechanical fan + pusher fan question

I have a 440 conversion in a 71 Dodge Dart 450-500hp. I found it ran hotter than I would like so this past winter made some changes. Large tube Cold case radiator, new fan, new water pump, new temp gauge, shroud is perfectly fitted around the rad and sealed against the radiator. Car has a 180 degree thermostat. When the car is moving, the temp is locked at 180 and never moves. When idling in traffic at temperatures in the high( 80’s / 90’s) the car is good for 5-10min and starts to creep up and will surpass 200 in 15+ minutes or so. As soon as the car moves at any rate of speed it quickly corrects to 180. The new setup is a major improvement but falls just short of perfect. I know that 200 is nothing but the reality is that I know it will not recover until I get the car moving. Coldcase has a shroud / electric fan combo for the radiator that I am sure will correct the remaining issue at idle. I am not not sure if it will fit in the space between the radiator and water pump. If it does not fit, I plan to try an electric pusher fan in the front on a relay that will on turn on when the temp rises (at idle). It should be off when the car is traveling at a cooling speed. ……….. looking for feedback from my Mopar brothers and sister who have experience with this challenge. Cheers Ron D