Johnny Copeland and Willie Dixon were two of them. Can't find their records, though.
Joe Frazier and Ernie Terrell had some kind of R&B groups going on.
Emile Griffith played the up bass?
Anymore names?
Bluesary Yours 8)
Ezzard Charles played bass and often sat in(technically stood in) with jazz groups. Jazz groups usually play the blues in some form so I think Ezz counts.
Ezzard Charles! A friend of mine, Harvey Cropper, used to be his sparring partner. Harvey PAINTS the blues and I remember his jazzy spoken stories about Ezzard. He hung out with The Bird to, Cropper.
8)
Willie Dixon was the Golden Gloves Champion I mentioned. There's Champion Jack Dupree who's reported as having had 107 fights and Roy Brown from New Orleans.
And by combining info from different sources, I've been able to find a fight for Berry Gordy (though not a Blues-guy).