Well I finally got back to this project.
So far I have added 4' to the main frame for a bed length of 20'. Added more crossmembers since the originals were 4' apart. I moved the tandem back one whole position, was lucky the rear spring hanger was in the right location to become the mid hanger, and cut off the old front hanger and rewelded it in the rear position. Also got a new rear bumper welded on, and also had to extend the width of the bed a foot.
I did the bed extension because we ended up buying 2 new quads since the original design that were a bit longer than the old ones and they were right out to the end of the trailer and I just didn't like that, so 6" of tubing on each side welded to the main frame and I'm happy.
One of these days I'll get some pics,,,,,,, hopefully before I put the deck on.