I took mine to radiator shop and they tore it apart, rodded it out, fixed a small leak, cleaned it up , put it back together and for less than half the cost of a new one. If yours is bad enough to need replacing, I've heard good things about DeWitts. I've known some guys to use BeCool from Summit that seemed happy with theirs. I'd look at some of the sponsors here on this site.
JIM! Dam bro haven't talked to you since CruiseFest '05! You should've come out to CO this year, we had a BLAST!
So what were we talking about here...oh yeah, radiators! :L I have a Dewitts in mine...PRICEY, but what a NICE unit! Unless you're having trouble keeping your engine cool, upgrading ONLY the radiator isn't going to do much for you (over stock). Like the engine itself....the cooling system is just that...a SYSTEM. If you want to "improve" the performance of the system, you have to address more than just the radiator....high-flow water pump, thermostat (a Robert Shaw stat is a very cheap improvement), air flow....yada yada. In addition to the radiator I have installed both the higher flow RS thermostat, and a Flowkooler water pump. At highway speeds the system works MUCH better, but with the stock fan I haven't improved air flow at all, and even with all of that once the car comes to a stop it's not much better than it was stock. In my case I have a trans cooler sitting in front of the radiator/AC condenser, so that is inhibiting engine cooling ability somewhat (as well as AC performance, pretty badly), but the trans stays nice and cool. Always a tradeoff!