It may not pass visual inspection for emissions in some states. I see you're in Colorado, so I know you have to get the truck tested once a year.
The reason is something related to exhaust has to exit the vehicle behind the passenger cab. Since our K5s are pretty much nothing but passenger area (no seperation from the "bed" of the truck and the cab), I think you have to have the exhaust in the stock location to pass.
I could be completely wrong, but I know someone around here brought this up in the distant past.
Definately find out before you get turned away from the testing center. Let us know what you find out too!