Having had both the US Gear and the Gear Vendor, I agree the US Gear is a much beefer unit. But it is not without its own set of issues. I was able to pick up a spare in NM for parts last year.
I built the 550 to tow my 5ver. My wife and I travel around the country while I work. Its a big truck in little truck disguise. if you look at my albums you can see some of the transitions for government mule to RV toter.
I had a new 450 pull up next to me the other day and the driver looked over at me with this "yeah its a 450 look". I had to laugh when his face sagged when he saw the 550 badges.
Hey, its all good
Barney

 

Ahhh big truck envy. I would drive a ranger if I could but I need a 3/4 ton or better. Got a good deal on my 550 and now am covered for the future. I only put 6-8000 miles a year on it so it should live a while. My daily driver is a 1996 geo metro. Hows that for a heavy hauler.

 

That would be nice. 6-8000 would be about 3 months for me. I've thought about buying a little beater for work, but that's another vehicle to insure and maintain. worse yet, Cheryl and I couldn't ride together when we're moving from job to job. And sometimes that's weekly Maybe I'll buy a big KW or Pete and put a Smart car on the deck in front the 5th wheel plate. What the heck, its only money, right?
That'll never happen. 1st-no desire, 2nd no money!

Barney

 

What about a 10k mod and call her good?

 

5th wheel needs to be a toyhauler with a little guest room/ garage in back for your golf cart I mean smart car.

 

In Ca it does not matter what you do to your rig you can not increase capacity beyond the manufacturers rating period.

 

A mild tuned 7.3 isn't going to benefit much if any from big exhaust.
Back pressure might be a slight issue on racing applications or giant fuel and air, but just for a mild tune and towing, I see no reason why larger exhaust would be needed.
Even if exhuast pressure could be lowered at peak output, you're rarely ever going to see peak output.

I'm not 100% sure exactly what you expect out of the engine, but theres a huge difference between adding a little TQ to a tow rig, and setting up a 3600 rpm dyno screamer.

If I was towing lot's, I'd stay stock, or ad maybe 20-30 hp or so. Maybe even just the 10k mod. As soon as you add more, reliability will decrease.

Also a home made boost fooler might give you more snap, even without tuning.

 

This is a mod where you hook up a resistor to the high pressure oil line, causing it to run higher pressure than stock.

It increases the TQ a touch.
I once drove around with a variable resistor attached, and a boost fooler, and that was enough to spin the tires, and send black smoke everywhere.
I don't know if there would be any danger of using the wrong resistor, or a variable one, as I did.

It does cause your engine to lope a bit, or with the wrong resister, barely start and chug black smoke while almost jumping out of the engine bay lol.

 

Bob,
One of the first things I did when I got my very used truck was to remove, clean, and rebuild / re-oring the leaking fuel bowl. Put it back in the truck and, oh crap, it was still leaking. Looked like it was from the drain vlv, heater plug area or so I thought. Tried loosening and retorquing these but no help. I then realized it was seeping from the cap and running down. Loosened and re-torqued the cap and no leaks since. Hope that's all yours is.