Rebuilt 318 Refuses to Start

I know it's getting spark. Swinger, I don't know much about carbs so I don't know what a transition slot is. Idle mixture I'm not sure what it's set at. I had the same carb and everything on the same engine previously before I built it and it ran fine; haven't changed a thing since then so I don't know why it wouldn't work now. I'm not running a choke but we have tried closing the butterfly valve to allow more gas etc.