I'm sorry but, I'll need a refresher.. are you wanting to prostreet the frame? Or, are you wanting to "un" prostreet the frame?

In either example, (if you're not building your own frame) you'll need to have on hand the subframe you'll be working with.
At least then you can get some measurements. There are prints of a couple ford frames found on the net. But they'll be pretty generic I think.

Do you have a frame table to work with? You can build a simple one from wood if needed. It just needs to be stout, flat and have places to anchor the chassis and keep it in a fixed position.