Header flange dimensions. (dxf)?

The mounting hole centerlines to ports vary from head to head.
Your choices are to make a cardboard template off the heads you will be using, or go with slot or large holes in flanges.
Are you a member of Speedtalk?
Photos in there of my build and on page 2 Calvin posted a sketch showing the horizontal placement for the heads of the 340 he was working on.
https://www.speed-talk.com/forum/viewtopic.php?t=42702