Doug looking at the back of the block can help tell you a few things. The 406 and 427 topoilers had the
oil pressure relief valve. Looking at the rear cam plug you should see 2 holes at 12:00, one ontop of the other. The bottom one should be a threaded plug that houses the releif valve. The one above it is the main
oil galley for the cam bearings and if still original would have a cup plug. Or it could have been changed to a threaded plug possibly over the years. The block should not be machined for hyd lifters and should not have plugs at the 10:00 and 2:00 positions around the rear cam plug. The block would not be a sideoiler casting. The block should have press in freeze plugs if original. If so you can remove a few freeze plugs and use Dave Shoe's drill bit test to gap the wall cores. Personally I wouldn't buy a engine I wasn't allowed to inspect. If you can post the pics you have it would be helpful. Good luck!