Try forcing some oil into the oil pressure port with a hand pump or a low-pressure pump driven by a drill motor. It's possible you've got an air lock in the pump gears and you need to get them a little wet before they will develop enough suction to pull oil up out of the pan. It's also possible, but not likely, that the pump pickup tube has gotten dislodged in the process of installing the engine.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!