That is some very in depth info. I believe that is what is needed, info wise and help in general to aid in the type of project addressed in the main topic or first question posted. In my opinion making two new frame horns would be the way to go. Use the existing frame to lay you're new frame pieces over the top of them. This would put you in a very ballpark (extremely close) position. Set the two new rails offset to clear the adjustment rods coming up through the new member. Using the existing rails as a layover would eliminate lots of measuring. Assuming the truck will be now be a lower vehicle you will drop each side the height of the existing frame and additional to the "drop" of the now IFS. With everything in place and measured you can lay the new front extensions, tack strongly in place, once held you can eliminate the old front sections and slide in the front clip.