Prior means earlier/before; I think maybe you have the dates incorrect. My 84 300D had 12mm x 1.250 threaded holes.
I thinkt the 10mm ones are on the latest Models.

Time Sert is not the only one available. Helicoils will also work. Helicoils are slighly less exensive and you do not need to enlarge the hole as much.
However, the Time Sert has a more elaborate kit.

If you want to see what kits are around do a search on eBay.

There is even a Kit that would work on VW Rabbits or My Volvo Diesel to renew the Injector Threads.

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84 300D, 82 Volvo 244Gl Diesel