[HO455]

Late last night my buddy Karl came by and this (Photo #1 ) became this (Photo #2)!
I spent this morning wrestling the 2 back underside supports into position. This became quite the battle until it dawned on me that I had replaced the body bushings and had tightened them down on 50 year old rotting wood. Once I had loosened the 6 mounts for the rear of the cab and jacked it up 1/4" everything easily slid into place.
I forgot to get photos of the router work to get the "Key" piece to fit up properly. I used a tongue and groove bit set to try and match the factory work. Thanks to Richard2717 for confirming how the factory did it as I didn't have much to go by. (Photo #3). It took me a little while to figure out what was supposed to be bolted to the indented rectangle on the bottom edge, but finally I realized that was the end of the front underside support. ( Which actually is the second row seat and seat belt plate and not a support piece.) No wonder I had to loosen the body bolts with that much crush in the wood.
The last photos are the "Key" piece.