7/32 is 5.556 mm 0BA is 6mm and as the Austin wasn't metric I would hazard a guess that you should look for 0BA
This site shows 3/16 BSF http://www.stainlessautomotivefastenings...ts_id=8824
Also 0BA raised countersunk
https://www.stainlessautomotivefastening...rtbd37r4j6
You can identify a 12-24 screw by measuring the diameter with a ruler at slightly less than 7/32″ (slightly larger than 3/16″ or 0.210″).
This site shows 3/16 BSF http://www.stainlessautomotivefastenings...ts_id=8824
Also 0BA raised countersunk
https://www.stainlessautomotivefastening...rtbd37r4j6
You can identify a 12-24 screw by measuring the diameter with a ruler at slightly less than 7/32″ (slightly larger than 3/16″ or 0.210″).