FWIW, Ron Davis himself gave a nice talk on radiators at the POCA Fun Rally Tech Session. One of the questions regarded single pass vs double pass radiators. Mr. Davis said a double- pass rad as used on Panteras usually gave a 17 degree F temp drop relative to a single-pass. This is what Team manager Carroll Smith also found with road racing GT-40s back in the day. Stating the obvious, Panteras cannot afford to give away 17 degrees of cooling, so always use at least a double pass! A triple pass gains a little more over a double pass, but not another 17 degrees- diminishing returns lowers any further temp drop to more like 5 or 6 degrees.
The main advantage of aluminum rads is 'as good' cooling as a copper/brass rad and about 1/4 the weight. My stock rad (probably with some hard water scale buildup inside) weighed 64 lbs, while a custom core copper/brass weighed 45 lbs. The Fluidyne (from PIM 10 years ago) weighed 17 lbs.
All three cooled adequately but the Fluidyne, because of it's much larger internal passages and the fact that it holds a little more coolant, dropped my cruising temps by 15 degrees with no other changes; YMMD.