5.29 gears is way to low for a diesel on 37's. On the highway you will have high RPM's.
I ran 4.56 gears and 38" tires on my 99 superduty. That set up felt good.

 

Ok. First off, you're not going to get any more power than what you have, regardless of who does the tuning. The stock injectors in your truck are keeping you from making more power. Then your turbo becomes a hindrance. You said you already have a HPOP, so that's taken care of.

The modification that will put more power to the ground would be a regear in the front and rear axles as others have mentioned. It's NOT going to be cheap.

Without injectors, you're going to be nowhere near 400 RWHP anyway so you don't have to worry about your connecting rods.