Whitehatter, the freight family concept did exist at Lockheed and it had plans to offer the -130, -141 and C-5 all as commercial freighters, However, like the C-17, no one could afford them but the military.
The -130 did make it into commercial ranks and even Delta Air Lines out of ATL tried for a few years to use the C-130. At the same time, oddly enough, they were also operating Curtiss C-46 freighters.
No one bought any of the -141 and as others have noted, there were plenty of commercial airframes that could be converted to heavy haulers which were faster, cheaper and carried more. The DC-8 is a prime example of this and many suggest that the only reason McDoug stopped building the -8 was to add a bit of push to the DC-10 program.