Was this engine running before you rebuilt it?

After reading the posts I'm thinking is injection pump timing.
If you dis-connect the transmission from the engine will it start?
Maybe the hydro is bogging it down.
Can you post the video on youtube?

I don't know much about diesels but maybe I can toss in my two cents..... I'm not sure whether if you have mechanical or electrical injectors. You seem to indicate that they are working, but are they working on run mode....especially with electrical injectors? It is one thing when you are in start, but what about run? And as some have mentioned before, is the timing correct?

@ 70 degrees it should fire right up after a few spins

I was thinking about the same lines. If I read right and the rings were replaced, was the front cover removed and then the timing set incorrectly? Were the shims that set injector pump timing reused or left out?

One thing I did not see anyone ask. Maybe it was asked but I didnt see. Air is almost as important as fuel on a diesel.. It there any restriction keeping it from getting air?