Master Cylinder Adapter

Are the dr diff ones 3/8 or 5/16 threaded mounting holes?
Wilwood master cylinders have a .420 dia opening and some of the "chrysler stlye" plastic reservoir types have a .34 dia hole.
What size should i make or should i do both?
Any other members interested in one of these?
Just measured the one I got Dr.Diff. Threaded holes are 5/16.