I recently had the brass/copper radiator in a '60 Valiant rebuilt with a high density core, where vertical tubes in core are on 3/8" centers instead of the OEM 1/2" centers. With the original round top radiator tanks it is difficult to go from two to three rows of cores. It can be done but difficult to find the talented (and willing) person to do it. Rebuilding the original radiator with a two row high density core was almost twice the cost of the typical aluminum replacement radiators out there. Also, rebuilding the original was dependent on the tanks being judged "good" by radiator shop. Decades of thermal cycling and repairs can make the unusable. In the end it comes down to originality vs. cost I guess. On aluminum radiators for SL6 cars, often the lower hose barb comes straight out instead of being angled like the original creating a potential hose/clearance issue. It's been a while since I installed one of these so maybe by now complaints have made manufacturers fix this.