Last Fall I bought one of those brand new Active Performance all-aluminum radiators for the XJ that are in the Quadratec catalog. I knew heat was always an issue with the XJ, and I thought it would work great to keep the engine nice & cool. I have an aluminum unit in my CJ that's made by an outfit called Be-Cool, and it works perfect.
All through the Winter it worked fine with no problems. Well, now... less than 8 months since initial install (and professional install, too) I have to replace it because the entire side weld seam blew out and it is leaking like the Titanic!!!!!! And of course it is past their 90 day factory warranty period, so I have to take it in the shorts! WOW!! Nothing like flushing $500 down the stool!!
And now of all times, as I lost my job 2 weeks ago when Chrysler shut down until... whenever. Crap. Anyhow, I opted to replace it with a genuine MOPAR stock unit. At least I know that will hold up. Maybe later I can look into one of those cowl induction hoods as an alternative way to help keep the mill cool. *SIGH*
Your mileage may vary, but please keep my misfortune in mind if you're contemplating buying one of these things.