Tony,
If $400 seems like a lot for a full set a detailed drawings, then you might not want to jump into this kind of project. Just the price of DOM tubing will be a shock.
By the way, DOM is "drawn over mandrel" a process that creates tubing without a weld seam like you see on most tubing. Much better mechanical properties but much more expensive.
But, back to the drawings. You will spend a ton of time trying to hunt down dimensions, take photos, and ask people questions. In the end you will always wonder if you got the motor mounts in the correct place, etc., etc. For example the frame rails are 17.50" on center not 18".
I would think starting from a correct baseline would be quite valuable.
Regards,
John