I personally have never seen a Crown RR/RD without sideshift. As far as adding one if it has been removed or did not come with one... I recommend finding a certified tech. Either a local dealership or independant service tech. As far as tires, you can shop around but try to stay as close to OE compound as you can. Many options and prices difference when it comes to options like freezer/traction, smooth, non marking, poly/rubber compound etc. etc.
The truck data # will tell you what it came with from the factory. You will need to get a service manual and look at the ITD section to decode the number on your data plate.