Head Gasket replacement.

My car had a back head gasket that was leaking. After replacing both head gaskets, put engine back together. Upon trying to start car, it will turn over briefly, then sputters and dies. No codes stored. I checked all vacuum lines, made sure the ignition wires were on the right coils, etc. It feels like the timing is off, but pcm is in working order. I did not touch balancer to disturb timing. Is it possible that If I put the wrong head on the wrong side of the block, that the valves are off, causing timing to be off? This really has me stumped.....Help.

Thanks,
Jim