When I changed mine (they weren't as far gone as the above BTW
) I ended up using the X300 style upper bush arrangement. The shocks came with the necessary parts which do away with the "top hat" bush, replace the steel collar with a thicker one, use a pair of much larger isolators and a pair of "deep-dish" washers with a more pronounced flat near the centre. A couple of years and 10,000 kilometers later, no issues.
This "improved" system would work on any earlier year shock, but of course you would have to source the newer bits individually as they only come with the later shocks for cars with X300 style cast wishbones.
The ones I took off had the disintegrated top hat bushes and at first I thought I'd ordered the wrong shocks because of the different upper layout but when I fitted them the isolation system made sense even though the top hat bush was "missing".
94 XJ40 VDP
Oyster Metallic/Doeskin on Aero Alloys
220,000 Kilometers/136,700 MilesDaily Driver
94 XJ40 SOVEREIGN
Diamond Blue Metallic/Barley
111,000 Kilometers/69,000 MilesParts Car