Only thing I would try that you are not is to be sure the cold start lever is Out all the way and give it half throttle when cranking. You sure all the fuses are good, each GP is getting 12VDC? Not just the block that breaks them to individual lines?
These are the types of problems that give one gray hairs.
You can clear any air from the leak lines by removing the cap from the end and pinching off the return line while the lift pump does it's thing. Wait until you have a clear flow of diesel from the last injector.
If you have the possibility of tow-starting it, give it a go. Level ground, a good helper, and a good strap should get the job done.
A tow shouldn't be necessary in my opinion, especially if this is a fresh rebuild.
My first thought would be timing.