I went ahead and made a drilling template from some .400 thick aluminum.
https://www.youtube.com/watch?v=YdkM...ature=youtu.be
I made the holes .266, a snug fit for my 17/64 bit to drill the new holes and then .303 for a snug fit for 5/16-18 bolt.
It bolted up perfect to the mounting holes for the 11 inch pressure plate. Then I drilled (by hand) two of the holes for the 10 inch and bolted it down. All the others look lined up well, I'll finish drilling and tapping the others tomorrow.