I have a 1986 Firebird and while it stays cool under normal driving, when I need to climb a long hill or put some load on it for an extended period of time, the temperature spikes and I haven't found a point where it will stop getting hotter without lifting (And I don't plan to). Does anyone have any affordable recommendations for radiators with heat capacity for 400+hp so I have some breathing room? It MUST be an easy install because the car is my daily driver as of right now. (Obv it's a V belt car because 1986)

For reference:
I am using 4th gen LS car dual fans with shroud on the stock radiator that was pressure tested and cleaned about a year ago when I put a new motor in the car, and I have a transmission cooler stacked on top of it along with functional Air Conditioning. My air dam is in place and functional.