The R-3350 was a very successful engine indeed.
But don't forget the UK's own Napier Nomad, for a truly complex compound engine!
http://users.bigpond.net.au/Shackleton/nomad.html . Shame it never entered service though!
My car has a supercharged engine producing around 110 bhp/litre. The supercharger is a Lysholm-type geared blower, belt driven through an electromagnetic clutch and a complex engine management system. It is seamless in operation, running at over 20000 rpm and 1.2 bar of boost, but only runs when needed, so avoids unnecessary losses. If the digital computer had been sufficiently advanced in the 1950s, I wonder what sort of SFC efficiencies would have ultimately been available from high-powered reciprocating engines with FADEC systems and prop management devices?