Backing plate seal and stud tool question.

There was a member at moparts who made various size cutters. I don't know if he still does. Annular cutter is about the same thing except they dont call out the inside diameter in descriptions. https://www.amazon.com/dp/B01BHJ6PYC/?tag=fabo03-20
9/16 deep hole saw with pilot removed will work too. Arbor and hole saw will be about 20 dollars.