Got a little work done on the mock up of the rear disc conversion. Used a piece of 1/4 inch plywood to make template. Drilled out the axle opening using a hole saw and then transferred the bolt pattern to the template using the bearing housing as a guide.
Used a nut to extend the bolts which kept the template locked into place. Then I used a couple transfer punches to mark caliper bolts.
Then I cut out the center with a 4-1/8 hole saw and trimmed and radiused on the belt sander. Next step is to build a pair out of 3/8 plate.