Hi David,
The original mount (and plans) were based on a '72. The early cars had a different restraining strap pattern. As you discovered, an adjustment needs to be made. The RT mount that Roostmonkey sells has both patterns built in.
As for the fore/aft location, the R200 mustache bar, when used with the R200, should run behind the rear suspension uprights (instead of ahead like your car came). This should land the holes in the correct location.
All this is just a tad late, though