BOP bolt pattern.
This should help you.
top bolts are at 7" centers
stright line from top bolt holes to center bolt holes are 4 5/8"
stright line from center bolt holes to the bottom bolt holes are 4 5/8" also.
The BOP will be 12 1/2" wide center to center on the middle bolts. The Chevy will be 15 1/2" wide on those center bolt holes.
9sec.