Oil Pump Assembly Too Tight

I am rebuilding the oil pump on my TO-30. It seems to be too tight when I put it together. Can you tell me what is wrong? November 1, 2014.

Here is a copy of the section on rebuilding the oil pump from the Dealer Shop Manual. I would wonder if the new shaft is properly seated deep enough in the casting and if the drive gear inside the pump is installed with the correct side facing the cover plate side of the pump. If the bushing is not seated deep enough in the housing it will push the drive gear up towards the cover. A problem can occur when the aluminum drive gear is not pressed squarely on the shaft of the pump drive gear.
It is also possible the shaft was bent when the aluminum gear was installed. You should be able to check this with a dial gauge while turning the aluminum gear. The dial gauge will have to be secured to the pump body with a fixture or magnetic mount. Try turning the drive gear with the cover installed and the driven gear left out and see if the binding still occurs.
The clearances listed in the procedure should also be checked. The proper gasket is also important. The original gasket was lead but the ones now are a black gasket material. The thickness of the gasket is important. Because the clearance between the side of gears and the cover is important to maximize pump output the clearance should be just enough so the gears turn freely.
It is possible to reduce the thickness of the gear that is too thick by using a lapping plate. A lapping plate is a sheet of flat glass machinists use to fit parts. Lapping compound or a piece of water wet abrasive paper of a very fine grit it placed on the glass along with some light oil and the part is moved in circles over the surface to remove a slight amount of material. Mylar backed abrasive paper works best and it needs to be a very fine grit and changed frequently for good results. You can find articles on this on the internet.