I own a 1970 C210K, and it absolutely can not be beat for economy of flight, speed, and payload.  The 1970 (not 1971) C210K has the highest useful load of any normally aspirated 210, before or after.  You absolutely can not overload it, and you can't load it too far aft even if you try.  I routinely fly my entire family of six, plus luggage (so full that it will not fit in a medium sized SUV when we land), and I am not at max gross or max aft CG.  We fly it lean of peak, so at altitude it will lean out to 13 gph.  Above 10,000 feet, you can fly for 5 hours and land with 1 hour of fuel left in the tanks, at speeds at or above 160 knots.  Most C210's flying today have the gear door mod already completed, to remove the landing gear doors (reducing gear hassles) and some have the nose landing gear mod that hard-links the nose gear to the doors (after the mod, the nose doors pull open and shut with the gear, rather than an independent door actuator).  To avoid gear problems, you can find out where each of the gear position sensor switches is in the wheel wells (a total of seven--one up and down switch for each gear, plus a squat switch on the nose) and spray them with electrical contact cleaner religiously every oil change (cheap spray is available at auto parts stores). Many gear "problems" are false alarms due to faulty light indications from gummed up switches.  If you follow that procedure, gear maintenance will not be any more significant than many retractable singles.  Our IO-520-L engine is still getting compressons over 70 in all cylinders, and we are more than 100 hours over TBO.  (We have a partnership in Dallas, and are looking for another partner.)  It is a real shame that Cessna doesn't make this airplane any more, because even the Columbia won't fill this particular mission.  The C210 is an amazing airplane.