Also, it's possible for the bottom of a pushrod to ride the edge of the cup in a lifter. This shows up as an adjuster that seems too far unscrewed. You can check this after dropping in the pushrods by being sure you feel some suction when trying to pull them up a bit from the oily lifters. As for seeing inside, I use a small-diameter, telescoping-type mirror. A bit fussy to get into position, but gives peace of mind.
All that said, it's pretty hard to guess at the cause of not starting without knowing the full extent of the rebuild and if it was running well before the head/rocker work.
Ricard L.