Considering the Ju-52 used essentially Geman built P & W R-1340s, which many cropdusters are & were powered by, as here in the USA. Many since the '70s have been converted to P & W PT-6 or Garrett turbo props, I can see a Ju-52 with the same turbo prop installations. Speed is not always the root of converting to turbo props. Many times it's the improved reliability & maintenance, as well as performance. An example is on the cropdusters, both the radial engine & PT-6 are 600 HP. In addition to the PT-6 allowing a much sleeker installation, an aerodynamic improvement itself, the PT-6 weighs about 1/4 of the radial. This equates to increased payload as well as improved performance & reliability. PT-6s also allow more flexibility in fuel choices. Jet Fuel, AvGas, Diesel, Gasoline & the like. The piston engine is limited to AvGas, or Gasoline at worst case. For PT-6s or Garretts, one could fair in the cowl assemblies from a Tucano.