Steering box interchange???

I recently took a power steer box out of my 68 Dart with intentions of switching to manual steering. When placing the manual steer box in place, I realized the mounting holes in the steering box were smaller (7/16" vs. 1/2" for the 68 Dart). I believe the manual box came out of a 65 Dart.

Have any of you ran into the same problem? Is drilling out the early manual box mounting holes to 1/2" the best fix?

Are there any other differences I should know about before I start drilling out holes? Will the 68 power steer pitman are fit on the early A-body steering box?

Thanks guys!