You are correct; they are outta a 221. That rod/bearing setup was used in the English 'V8 Pilots'. Those bearings nowadays are impossible to find. All is not lost however; The American flanged full floater style bearings [1932-38] will be a direct replacement. One advantage with using those existing rods is that, generally, because the previous bearings are the 'lock in' style, the big ends of the rods tend to not be worn oversized/oval, as happens with full floaters. Consequently, generally you can run floaters with a standard size o/d. Obviously, measure everything up, don't worry about the double oil holes in the journals; the floaters will run quite happily on them.