this is what I have they are .187 dia with a setscrew. You can drill-em out and re-tap.I also have a solid shaft that I have no use for as well as 2 needle bearing that fit 5/16 copper pipe.
They may be heat treated, the dog bones You need a OC810ML male end of a U-joint 1/4 ID 7/17 OD with 2 setscrews I think bit I may be wrong as what you want.
Where is this going into.?