If you can't find a stable version for 1.43, consider these alternatives:
Since ETS2 is now on version 1.50+, finding a stable "piece" (or compatible file) for the older 1.43 build requires looking through specific mod archives: Key Features of the 1.43 Offroad Mod
Place the downloaded files into Documents/Euro Truck Simulator 2/mod .
Includes specific off-road trailers designed for rough ground.