If in fact it was a UJ causing the clonking noise, there should have been a lot of vibration felt before it got that bad, from the pics i dont see any rusted parts or abnormal cavites ect,

Spose the noise could have been coming from the front, some transfer cases run UJs to the outer CV joints,

Ah well, none of us were there, so we will never know,,

If its Isuzu,the Engine Outclonks any CVJ or UJ.