64 225 slant 6 motor rebuilt, won’t start…

Problem with starting engine, it has plenty of spark and gas, cranks over, but nothing???? Do these motors have a oil sending unit on them that will kill the engine if not enough oil is going to it? Also this motor has everything new on it, from the starter to the fan. The first time it did anything when cranking motor, it back fired thru carb with a nice fire ball!!!

Any suggestions would be nice, this motor is in a 64 Dart convertable frame off restoration.

Thanks,
Metalman