Rebuilt Engine Installed, Won't Start
 

Bought a remanufactured engine from a shop with a good rep (not in Washington). Took a lot of work for my guy to get it and the new RB headers in, and it won't start. I had an LS2 ignition system in there and he wasn't seeing spark so we switched back to a factory coil system. Now we get spark, and fuel, and it cranks like a bat out of hell and compression seems good....but it won't fire. He deflooded it just in case and all we get is some burning of oil coming out of the exhaust.

I think he checked the ECC, but other that that, is there something we're missing? I've been driving a rental for WAY too long now.