I was blessed to have caught the last gasp of round engine flying in the lower 48 , from 87-99,my Ernie Gann/ St.EX fueled dreams were realized, flying DC3s and Convair 340s out of Michigan,Ohio, and Pa.to everywhere imaginable from the frozen north to the Sierra Madre, it was hard, beautiful work, and it has been completely taken over by turbine powered ships. I think Catalina flying Boats out of LGB , is still running some round engined 3s, I think the museums and preservation societies are your best bet in CONUS, but the radials are making a last stand in AK, and the Carib,where everything from DC7s to C46s are still earning a living, God bless them !