May be time for a new engine, usually when the liners are low its because the block is worn at the bottom where the liners sit, you could try removing and resealing but likelyhood it still wont be right, also may find the head is now over skimmed, a second hand k series may be the best bet now.
There is a chance the older style gasket may still seal it, but as din says the metal ones arent as good as taking up larger tolerances.
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