Has anyone used the Mark Williams C-clip Eliminators on their 12 bolt? Seems like a much nicer kit than the others that are available and uses a much larger bearing. Looks very similar to a ford 9 inch type set up once installed. Here's a link.

http://www.markwilliams.com/detail.aspx?ID=794

Also, has anyone successfully kept the operation of their drum parking brake with an eliminator kit?

It's a larger bearing than normal, but it's still likely going to leak. Moser also makes a c clip eliminator with that size bearing.