Hello GT500. I found a few articles on the Net with tips and photos that may help you with the renovation of your Stang. Apologize for the delay in replying to your email. I was away at a college football game for a few days. One of the other site admins had to leave his home because of Gustav.
frame repair and strengthening, includes photos
How To Repair 67 Mustang Frame Rails
frame rail replacement discussed in a forum for a 67 convertible
Frame rail replacement - MustangForums.com
well written article with text and photos focuses on the tools that are needed to do the repairs for 65 and 66 stangs
Rear framerail replacement on a 1966 Ford Mustang - Mustang Monthly Magazine