42RH / A-500 in a Duster with pictures.

I would make a 1/8" thick piece of metal in a shape that completely covers the hole and either epoxy it in place or drill and tap a couple of holes to screw it to the housing. That way you don't get oil slinging all over the place as the seals wear. The screw holes don't have to be very deep since the screws don't have to hold much.