Just a thought but maybe the gaskets and seals are not your problem. Check the mating surfaces for cracks or defects. I have seen where a seal has been removed and its bore has been gouged by the tool used to remove the seal. Look over the timing cover carefully and make sure you have no cracks and if any bolts pass through, use thread sealant on them.

Another thought is the dampener snout. Did you test fit the crank seal on the dampener? Is the dampener snout free of wear marks?

Best of luck.