MSD distributor

I am looking at a MSD pro billet distributor #8534 for my 70 340 Duster. What is involved with adjusting the mechanical advance? Also I have a Rev-N-nator ignition box, would that work instead of the MSD box that says is required? Right now I have a mp electronic dizzy, but it seems to have about 20-22 mechanical advance and I don't feel good about trying to weld up the slots to limit that.

Thanks