I appreciate the suggestions.  I ended up starting with 320 grit wet sanding; this produced a very shiny surface but was removing material very slowly.  I used 220 on an orbital sander and sanded for a few seconds, checked, sanded, checked until I had a nice uniform surface.  I could still see a couple of scratch marks from the rotor, but I couldn't feel them anymore.  I did a bit more 320 wet sanding after that and called it good.

Unfortunately, after test running the engine a moment ago, I am getting seem oil weeping from the plate seal.  The gasket provided with the kit was rectangular-sectioned.  I took care to install it with the wide part of the rectangle flat against the bottom of the groove in the pump body.  It did not want to lay this way naturally, so I had to slide the cover into place and then bolt it down to ensure the gasket didn't twist.   

Was I supposed to install it with the narrow side against the pump body?

Update: After several attempts, I was able to stop all leaking.  The gasket did indeed have to be installed with the narrow side against the pump body.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

yas i was original owner of the 55ford. I also mentioned ind engines, as  in canada all Y blocks  for Canadian as well as Australia wher assembled in  canada
YOU ARE probley aware that 1955 was the 1st year for y blocks in canada (my 55  was a meteor),same as ford except for  the grill. 54 fords had flat head  engines and the cars wher on same chasey as 53us cars. gear pumps where not quit as efficient  as  geroter pumps, but lasted longer..gerotor pump in newer ford engines wher fine as in the oil pan minor leaks not a issue.
hope ther are some older Canadian who worked in winser ford plant can offer some history

  Realy dont know what to say about the last response ??

Were you the original owner of the 55? Industrial engine? I thought we were talking about motor vehicles. 

depending on year,55ford I had was cast iron pump,,industrial engines had cast iron pump. 

The original Ford pumps were aluminum gearotor. The Melling pumps are cast iron, but not gearotor. Ted had/has some aftermarket cast-iron gearotor pumps. I discussed this with Ted a while back. He did say he prefers gearotor pumps, said nothing about the aluminum pumps leaking, and was expecting a shipment of the aftermarket pumps to arrive any day. I think he said the cost would be $240. Although my aluminum gearotor looked good, I went ahead and purchased the rebuild kit. 

gear pumps are less likely to leak at gasket as cast iron more stable than alum.i have a alum pump3years old and is always driving,when over tightened they warp. I have a new gear pump waiting to install

Check current price. Price shown is just $4 more than new M42 from RockAuto. The new pumps are not gearotor-type. 

If you call them, I would guess they could provide that information.   My crank is standard.  I run 10w/30 oil.  My oil pressure idling hot is about 20 lbs. Driving is about 45 lbs. or so. Here's what their website says.

Blueprinted Melling Ford 292-312 Oil Pump. Fits all 292-312 Ford Engines.

MELLING BLUEPRINTED OIL PUMP. The pump is a brand new Melling M-42 Pump Blueprinted by PRECISION OIL PUMPS. Fits all Ford 292 -312 engines. Each pump is disassembled in groups of ten, casting flash is removed from all passages, passages are radiused and blended by hand. The Housings & Gears are then Deburred by a vibratory polisher then cleaned. The Gears are then sprayed with TECH-LINE moly-coating and oven curred. Three Critical Clearances are checked on reassembly;(1) Gear to Housing, (2) Mesh or Backlash, (3) Gear to Cover-Plate. With Ten gear sets to choose from , One pair with correct clearances will be installed. The relief- valve is De-burred with emmory cloth ,cleaned and is re-installed with the existing spring and new hardware. Each cover plate is also Vibratory Polished, cleaned and fastened with safety-wired aircraft bolts. All pumps are bench tested. Buy with confidence.

---

Phill. It would be nice if they gave attested pressure on those pumps. I know engine specs and assembly also play into it but it would be nice to know where the bypass spring opens.. 

56 Vic, B'Ville 200 MPH Club Member, So Cal.