In cab; antirust coating, Dynaliner-Max or maybe try a Fehr kit made for a Case Unimog
Replace headliner:
Caterpillar Sound proofing, or upholstered coned foam
Refinish Dash board
Replace Speedo with MPH and install new gauges: Oil Pressure, Engine Temp, Exhaust Temp, Trans Temp
Install switches for new systems and replace any existing switches possible with new type