6203DW Bearings Wrong Bore? 16mm not 17mm?

[RRack]

I'm rebuilding my brothers old Aqua Flo 06620500-2 pump and ran into an issue with the bearings. I removed the 6203DW bearings and ordered 6203Z C3 17x12x40 bearings thinking they were identical. Well, the bore on the new ones are slightly too big by about 1/16". I'm guessing this particular bearing is a special slightly smaller bore at about 16x12x40? Why isn't this a different model number. Any idea where I can find the correct ones?

Thanks,
Robert