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From the photo's I would be strongly inclined to strip out the timing case as a motor in that condition may well have spindles that are also badly worn. And if you are going that far a complete disassembly , clean, inspection and careful reassembly using sound parts as needed would be in order.Hi photos attached show ATD, Cam and followers, the surface of the followers is worn I guess the hardened surface is worn away, the MK1 Cam end is best described as lumpy worn in ridges. The ATD looks ok apart from its movement being stiff, I note the comments made above, it will have to come off to be certain there are no problems, Given what Vibrac says about alloy idlers mine look pretty good and am now minded to keep them unless better advice comes forward. Remember that for most of its life this old gal from 1954 has been in a museum awaiting rescue.
Fear not, it is something you can do yourself there is no need for any fancy tools.
I am not suggesting that the following will be needed but about the only things you will need to get a engineering shop to help with is renewing the valve seats and or valve guides and rebuilding the crank assembly if there are issues with the big end bearing.
Work slowly and methodically making notes, labeling parts and taking lots of photos. You will gain great satisfaction from the process.