Instead of drilling and tapping your sump for a brass barb fitting why not send your sump to us and have a proper AN10 (or any other size) bung Tig welded in.
You can post us the sump and we will weld in an AN10 male bung and send it back to you same day.
We can also blast and paint the sump for an extra cost.
Price does not include return postage.