Radiator core addition cost???

I picked up a new 22" A-body "Heavy Duty" (318 AC or 340) radiator for about $140 at Advance Auto. My 360 (~370 HP) will sit an idle all day long in 90+ degree heat and the gauge won't move at all past the point the t-stat opens and starts to regulate.

FWIW, I am using a stock thermostatic clutch fan without a shroud and a stock replacement water pump.