I've found that if the steering stop is knocked off, then there's a good chance that the frame is bent. Find a surface that is as close to perfectly flat as possible, place the main frame (no lower rails or anything else attached) on it and see if the front engine mounts both touch or if one is up off the surface. Frame may rock side to side as well.
Found a couple of flat spots and tried a few different orientations, feels pretty square to me. If I do get wiggle it's less than 1mm or even less if I move it around to find a happy spot on the floor, so I'm going to call that the floor.
Removing the rear drive from the swingarm will not disturb any shimming - that is all inside the pinion carrier which should stay inside the rear drive housing.
If you're having the swingarm powdercoated, then all of the bearings (pivot and u-joint carrier) will need to be removed. The carrier bearing should be replaced anyway.
Ok, easy enough then - will do on the carrier bearing. I was able to push the vin-plate rivets out from inside the steering neck and I didn't even lose any!

Any other specific tips on dealing with the powder coater? They have done quite a few bikes so they know their way around - but sometimes overconfidence gets in the way (or unfamiliarity with Guzzis) and things that shouldn't be coated get buried. I kinda don't want to take the steering head lock out (I do have the key), maybe that's a fools errand it should come out anyway?