Here is the pics so far....

This is the way the seats were held in. 2X4's bolted to the floor...seat rails nailed to the boards.

This is the 77 seat sitting in it.

Here is the bumper that is going on to the 69. It needs cleaned up...and straightened a little on each corner.
The cab is temporary. It will be changed. Its in way to bad shape. I measured the brackets on the 69 from frame rail to frame rail...they exactly the same. The 77 bumper has several holes in the brackets to accommodate the 69.