I get a similar sounding clink/clunk from the rear end on my '74 4/4. I'd have thought it was worn washers in the diff (had similar with my MGB) but it's only done 11,000 miles (which I believe). So unlikely to be wear somewhere. I don't know the suspension arrangement of the OP's car but maybe tighten up the U bolts holding the axle. This has also caused rear end noises from my MG which has a similar rear axle setup as my 4/4.
