What would be quicker...
 

What would be quicker, a manual 7.3 with exhaust intake and 140hp tune or a stock 6.0 automatic?

Depends on how good the driver in the 7.3 is I'd guess. I'd probably still give it to the 6.0... What's a tuned 7.3 put down for power? A stock 6.0 should be around ~250-270rwhp stock.