To add to Rotty's excellent post, there's an interesting article in the latest issue of Aeroplane Monthly (latest for me, I just bought it) of the Basler BT-67 turboprop conversion.  The plane is in current service around the world, as a cargo carrier, fire fighter, all around everything ....  and as a cockpit photo shows " ... the glass panel belies the airframe's age, which can be up to 65 years old!" ...

The DC-3/C-47 is one of those few planes of which can truly be said, that the best replacement for it is another one.