cranks but won't start?

I would get a scan tool on it check for codes and check the data ,ECM relies on sensor inputs and you could catch a bad reading on scan tool data (IAT and CTS temperatures and MAP are the big 3 I believe for fuel control) , Incorrect inputs could cause a lean no start .

Of course good grounds and battery volts to the ECM need to be good and checked first . ( weak battery can cause lots of problems too)

Sounds like its lean, low fuel pressure/volume or bad input from a sensor ,or sensor connections .

Usually you find in engine swaps grounds left off /loose or pinched wires are common things .