Well, got the job done. For anyone else who needs this information. The flare nut oddly enough was 9/16. A 14mm slipped on me. The hex on the hose end is 16mm. The banjo bolt on the other end of the hose going into the caliper is 11mm, and the bleeder is 10mm.
98 Riviera SC3800 All stock except gutted air box.
1970 Buick GS455 Stage1, TSP built 470BBB, 602HP/589TQ
Best MPH, 116.06 MPH, Best ET, 11.54