Hi Tom,
It has been measured for center to center alignment and is within tolerance. I'd need to research how to measure parallel. If it were not parallel, I'd think the center to center would be way off. I will look around the internet and see what I can find to measure and/or consult some experts here on the forum.
The block the scatter shield was measured against had an offset of .011. The Ford maintenance manual shows a max misalignment of .014. For this pairing, I'd recommend a .014 for dowel pin offset, which should bring the alignment to near .003. The offset pins come in .007, .014 and .021 inch. For performance applications, I have read the recommended max misalignment to be less than or equal to .005 inches. This offset pin would make in less. But every block is different, so that is why I recommend it would need to be dial in to the block and crank it is being paired with to minimize the offset.
I will get back to you.
Thanks
Cory