It seem the ones I have are .003 to small on the outside diameter to fit correctly in the case bore. Has anyone ever put brass shim stock strip with pump oil port holes cut out and installed the shim around the pump when the engine is being assembled. Skip the o-ring method.

Pump tolerances have sucked long time sailor.
Return it and try another pump.

I O-ring and install before I tighten the case halves.

I would never use shims like that....you may as well fill your oil galleys with RTV and get your engine failure over with.

Schadek pumps vary from batch to batch.. Cases also vary by up to .005"

When I sold my billet pumps, I had standard as well as plus and minus sizes just to accommodate the case variables.

Always measure your case bore and oil pump warm, else you won't be seeing the full picture of fitted clearance during operation.