Small Block Mid Plate Specs

I'm building a rod and want to mount the small block with a mid motor plate. I know guys sell them but I need to make mine custom for the frame. I have use of a mill so I can make the plate I'm just looking for the specs for bolt holes and dowls. As a matter of fact I have the locations of the top 4 bolts I just need the specs for the dowls and lower bolts.

Thanks in advance for any help.
Author: MONC440