If it's indeed a High Rider as it appears to be, it's uncommon for sure... funny that mine and yours are both Georgia trucks.
I voted No, being a High Rider is uncommon but I am doubtful the Shotgun Customs thing makes it any more rare simply because there are a million custom shops out there that build 1 of 1 vehicles. It also appears to be a more or less stock High Rider, minus the bumpers, light bar and interior, with an additional appearance package. Curious to see what's up with the engine mods - it would almost be worth pulling the engine and tearing it down to see if it has had anything done to it for performance.
Don't take any of that the wrong way - it's a VERY cool truck and I hope you keep us posted as you dig into it!