Pretty sure diameter is different if you buy a complete bottom end gasket set made by payen it will come with liner seals in all thickness
810 engine was 1289 cc used in R10 R12 and R5 1975 -1980/1
Guess some of the continental suppliers should have them listed
I am happy to report that I was able to find workable gaskets. If they don't come with the p & c set, sadly, one can expect to pay about £ 12.50/gasket over here. C'est la vie.