A direct bolt on would come from another like model truck. Even then, if there is a different optioned rear, the mount perches may not align. There are a few things to consider when looking for a replaceemnt rear to be sure; Check the mounts for spacing and angle the the centerline of the gear pinion. These are the 2 things that align the rear and set it at the proper angle to the driveshaft.
Check the Pinion yoke and make sure it is the same so your driveshaft will fit.
Check the pinion length from the centerlin of the axle to the yake to make sure your driveshaft length will be okay.
Check the rear brakes for size as they differ depending on veicle
Measure end to end of the rear end assembly for wheel clearance.
Make sure the gear ration is for the type of transmission and set up you have. A manual transmission requires at least a 3.0 to 1 ratio and Automatic trannys are usually 2.5-1 or so. Large tires require a larger ratio. Some large trucks have 4-1 or 5-1 gear sets to get the big tires rolling.
If you find the right rear and the only thingis the perches, you can always have the originals knocked of and welded on.
Hope that helps.