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The oil galley is around 1 1/2" down in the hole, the threads are only about 1/2" deep, so the bolt has to be cut off around that length. You can go to any parts house and get a pack of brake hose copper washers. I got some at our local auto zone. They are on a turn stile by the brake odds and ends in a bubble pack, if they can seal brake hose pressure it can handle this. Remember it doesn't have to be ABSOLUTELY leak proof as the oil well just be dripping back in the oil pan as the squiters do.
You can run a nut on the bolt before you cut it and run it off after the cut and it well clean the threads. Then just grind, disc sand or file a taper on the cut end and if you have a bench grinder with a wire wheel use it to really clean it up.