I cant find it, but there is a very intersteing comparison ref aluminum vs brass radiators.
Ive done the aliminum raditor thing in the past:
If you were running hot to begin with, and the prob wasnt related to a shot radiator, an aluminum radiator will not really show an improvement. You get less unsprung weight with an aluminum rad, but no real cooling advantage. In other words, a in good condition brass OEM radiator cools almost just as well as a aluminum radiator
You are loooking at the key though: A shroud is mandatory for efficient cooling. I wont go into electric fans, etc. but you need to run a shroud, regardless
But if your original cooling issue wasnt related to a shot radiator, you wont see much improvement even if you install a shroud on your new aluminum one