There numerous part changes between the 1981-1982 models and the 1983-86 models, but you need to have a parts manual to identify them as such.
For instance the exterior decals changed for 1983-1985 on a Renegade from the 1981-1982 scheme so this is one external reference which COULD identify the model year, but it is just a sticker than any bozo could put on. They introduced a side stripe on the tub and the bonnet stripes were now in a small U in the dead centre of the bonnet (hood) instead of around the edge.
The substantive changes were in the engine compartment and drive train. The emissions controls etc. were beefed up but then they were under constant change from 1981 to 1985. The most obvious change was to introduce a wider track on the axles from 1982 as mentioned above and a large number were fitted with dana 44 rear axles as the AMC20 supply dried up, supposedly only in 1986 but some were fitted earlier apparently.
PICTURES, PICTURES, PICTURES.