Oil pan seal replacement

Usually the oil pan is pretty much secured with the minimum amount of bolts as the engine and pan flex a lot. If it was me and I wasn't super worried about being original but being functional I would get a bottoming tap in the correct size. Run that into the bolt holes and then use carburetor or brake cleaner to flush the holes out very well. Most holes are deeper than needed so the engine can be assembled faster. Now take two bolts of the same thread but longer and two nylock nuts. Cut the heads off the bolts and dress them of any burrs. Next coat each bolt with a coat of epoxy like JB Weld or similar. Then screw them in as far as they will go. You want just enough extending out that the nuts will engage fully. Let the epoxy cure and install the nuts. Using the tap first will clean out any remaining threads and possibly cut a few in the bottom of the holes. You will want to test fit the bolts to ensure how long you need.