Fascinating. I've never seen any kind of numbers like that so thanks for sharing! I'm definitely trying to keep it all tighter than that, but will all the adjustments I'm building in I'll probably be fine. If not I guess I'll build it all again. Haha.
I found 3 different holes that match on each frame rail. That should be enough to get me going. Thanks to you, the new plan is the use two layers of steel plate to form a main crossmember with a tube on each side running back to tie it in. I'll try to keep this updated as I go along this weekend. I should make way more sense when I post photos.
You can use the body mount holes if they are in the same place as well.