Maybe you can find a seller that has both and can accept returns. If not, backplane is the first logical choice, then the PSU.
So, I guess some good and bad news. After installing the new backplane I placed the single CPU tray in and the computer fires up. Sadly, and as expected at this point, the dual CPU tray didn't work. Fans kicked in. Other than having to test the wifi card I reinstalled and getting a new dual mini 6 pin to 8 pin for my video card (the one I bought had some loose wires) I will be running.
Now, I guess I have to bite the bullet and buy a new dual cpu tray and put my cpus and ram in there. Seem logical?