Hi Naj. In response to your question, I believe the primary benefit came from the Ron Davis radiator. Although some people refer to it as an engine cooling "system". All that means is that it is a package, which is composed of the high-performance aluminum radiator, with integrated water-cooled oil radiator function, 2 high volume SPAL puller fans, a precision-fit shroud, along with a little bit of intelligence in the form of electronics for controlling those big fans. In terms of engine cooling, the only other thing that had been changed (previously) was the addition of the M-B recirculation kit. I am running a standard mixture of M-B coolant & water. (I had tried water-wetter and the like previously but saw no benefit).
I should point out that I had the alternator upgraded to 160 amp (constant output) and have changed the car's wiring, etc. to handle all the increased power draw(s). Things like those big SPAL fans for the engine, plus another SPAL unit for the A/C blower combined can pull approx. 80 amps (and that is just 3 fans). And then there are 100W headlamp bulbs, Webasto seat heaters, seat coolers, back messagers ... well, the list could go on. But it tends to greatly aggitate a few folks, so perhaps I should stop there on the long list of added power consumers / creature comforts.
BTW, it was another hot & sunny day in Boise, Idaho, at 102 F. I ran a few errors around town; top-down, but with the A/C blasting and the Webasto seat coolers (modified) it was pleasant ... this from a guy who does not like heat, and who was forced to set through several minutes of dead-stop because of road work - but the engine temp held steady.
I've heard it said that a properly set up W113 engine can hold temperature and will not overheat. But I have my doubts about that and have been on a quest to just make the issue of one overheating 280SL go away. So far I am encouraged.