you mean you can't get R44 plugs anymore? first they discontinued the PF35 oil filter, and now this..
as for those plugs in the ebay link, they would work perfect in a mild 350 with Vortec heads on it, and are readily available at ANY parts store in the country. and you should be able to also get old gasket style R44 plugs anywhere, as well..
you don't plan sincerity.
you have to make it up on the spot.
wanna hear about 20 years ago when i was too smart to know any better?