Thanks you'se guys!
Check this out... I was looking at the cab floor today and I can't believe I never noticed this. The pics show the front drivers side outboard seat bolt hole. There is a good sized dent there where the seat bolts to the floor. After some research and also looking in my 1972 GMC parts truck, this area should be flat. Apparently hitting a ditch at 45 MPH with a 245 pound dude in the seat can do this.
Wow... no wonder the frame was bent.
I also have a dent in the upper part of the drivers side door where it hit my left elbow. How it didn't shatter my arm is beyond me. That area is pretty stout right there where the metal starts to round off towards the window opening. My arm was pretty sore, and I consider myself dang lucky. I am leaving the dent there, and have a pinstriper do a 1970's style asterisk in the middle of the dent with the word "OUCH" next to it.
Gary