Since the inside of the new drum is shaped differently than the old one, it might not be possible to use the sheet metal grease deflector shown in the inside view of your old drum/hub assembly. The fluted areas might not fit the smooth center of the new drum correctly. I think you'll find that both bearing races will mount into the outer portion of the 3-piece assembly that's held together by the studs. If so, leaving the sheet metal part out won't affect safety or the fit of the bearings on the spindle.
Jerry

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