I found that the best way to measure the rod length to 40.125 was use two 123 block to set against the ends of the rods.
The plans call for the rod ends to be 90 degrees from each other so one end was placed on a parallel to raise the rod end on its flat.
With the control rod trapped between the two 123 blocks the rod end could be measured more accuratly. The small angle block on the right was used to check the flat for the other end.