Well, got a little bored and decided to keep lapping. I used some #45 diamond compound suspended in grease for the bulk material removal, then #15, then #6. I half expected to use the bolt head as a sacrificial lapping tool as I figured it would loose as much material as the receiver lugs. It probably lost .005", but has a decent ridge on it at about the bore of the raceway. I think I'll go ahead and spring the $20 for a new bolt head from Midway. The integral lugs are much more uniform and have a perfect surface finish now though. I'm satisfied.

I did all this after building the spider setup. I'm half glad I don't have to use it. The mill I have access to is pretty worn. The bolt holes are a little skewed in spots, but that really doesn't matter much except for aesthetics. I do intend to build the mandrel that screws into the threads and butts up against the integral lugs. That'll give me a chance to face it off like the pic above.