Well Gang,
As SMLRanger says, go copper/brass over aluminum. I know the threads a bit old but, I thought I'd throw my 2cents in. Long story short, I had a leak, on and off with my aluminum radiator in our '04 Itasca Horizon 36GD with the C-7 330HP CAT. I found I had clogged fins in both the radiator and the CAC.
So, I pulled both. That took me around 6 hours, plus or minus 'cause I was not in any hurry. What I found was a bad section/flange where it couples with the plastic tank in the lower left section as you looked at it from the rear of the coach. Well, I figured I might as well roll over and play dead because I pretty much figured I'd have to empty the bank account on a new radiator from Freightliner.
Well, they had, at the time, 7 of them in Memphis TN. The cost, $1,842.00, without SHIPPING AND TAXES. So, off to a local shop I went. They said, that radiator is junk, throw it away. They said "Don't buy one from Freightliner, buy one from us. And the reason, it will be a Copper/Brass one that can be repaired at a later date, if needed. And, the cost, for the exact same radiator in size and shape, was $1,250.00 OUT THE DOOR.
Now, we've been on a few trips in some fairly heated conditions and, to be real honest, there is "0" DIFFERENCE in cooling. It runs the exact same temp, in various conditions as the aluminum one did. So, to those who may run into this kind of situation in the future, without a doubt, go with the Copper/Brass unless some one GIVES you a new aluminum one which, is probably not likely.
Scott