Just to beat a dead horse, an aluminum radiator actually cools worse than a brass/copper radiator. The best reason to use and aluminum radiator is for less weight, and most people think they look better. The main reason they have been made of aluminum/plastic since around 1980 is they are MUCH cheaper.
I call BS! My last 68 dart, hot 360. Somewhere around 435hp at the flywheel. I could NOT keep it cool at all with MANY different copper/brass radiators, fans, shrouds, pulleys. You name it I tried it with no Difference. I bought a cheap Ebay aluminum radiator, no shroud. It never went above 180 degrees! I'm a believer. I literally tried every combination of parts and couldn't get anything to work. I bolted the aluminum radiator in it with a factory clutch fan and it NEVER ran over 180 again. I drove that car to the nats that year and it was one of those hot weekends and I beat the eyeballs out of it and had ZERO issues.
I am talking proven science, not anecdotes, glad it worked for you. I have no idea if what shape the radiators you tried were in, and you probably didn't know either.
I put a Champion in a 340 Dart convertible, it was not a bolt-in, had to drill two holes and the quality was not great. Sure it was cheap, that is the point of aluminum radiators. I am sure it worked great, I never drove the car as it was a customer car and he never got back to me after he got it.