Glad to hear it, I'm still not running one on mine yet so I'm a bit of a hypocrite but I don't run slicks. If you need any other info about the trans just ask, I'm one of the few that hasn't gone through multiple 5/6 speed transmissions and I've been making a good chunk of power for a while now.
I ran my nitrous kit for years on 2 different trucks (one had 4.56s) and I never had to change gears so I can't imagine where you seem to think it's a requirement to do that. A 3200 stall converter and a 2800 stall converter respectively was used but I never had to do a gear swap and I was still passing the line at the top of 3rd at 6000 rpm with the 545rfe and a 105mph trap. A basic nitrous kit will get you down the track just fine and I've run a straight 150 and 175 shot respectively, you don't NEED all the other stuff, but it does make it safer and more consistent. A purge, bottle heater, progressive switch, fuel pressure cutoff, and any other accessories are great to have but not required. Add every nitrous accessory and you're now at $2000 and ~$100/refill. That's still less than the starting price of a ported head/cam swap with no supporting mods or upgrades with an average gain of 75hp.
I'm actually swapping in a set of 4.56s with the new blower package for more torque transfer; I'm getting away from the top speed build and going for a fun around town build with boost, nitrous, and water ****.
A 150 shot took a full second (0.94) off my quad cab 4wd's times even with cam, heads, full bolt-ons, converter, and 4.56 gears in my '07 with the stock 545rfe running 28" drag radials. It was a dead shot too, all of it off the line, no progressive controller.
You should try it, it's fun, but since you've never done it doesn't mean that it can't be done or that there's any reason he can't. Plenty of trucks run nitrous and higher ratio rear ends.
I'm not a salesman for any company and I still recommended nitrous for this guy. I don't run a cam from either Matt or Jay and won't have Jay or Sean tune my truck, if anything, at this point to avoid the BS since both would do well by me if I asked. The reliability of an everyday driver with stock power around town with an extra 150hp for track days is hard to beat, especially with the 5/6 speed trans which you aren't factoring a replacement cost into the head/cam swap cost. The trans holds a 150 shot at WOT just fine, but an extra 70hp around town is where things go wrong if you don't drive it properly.