It's a little difficult to see Norm ,I can't see the plastic ring but it could have if its not the short shaft motor.
Best one I saw was someone cut out a notch from the high arch to fit the briggs tank - bloody nice alloy deck as well
Reminds me of the alloy SupaSwift base I bought Tyler that had a Briggs ,they did the same thing cutting the
base for fuel tank clearance except they screwed a sheet metal plate under the base so the hole was covered.

Cheers
Max