I have looked at other trucks on the lot and found a large gap, so I thought it was normal. Maybe the differences are in the cab and box configuration.

Mine is a Crew Cab with 5.7' bed. - Large gap don't have access to truck since I'm out of town.

 

I have a large gap too prob a tad over 1". The rubber does not touch and I was wondering the purpose too. I am wondering how well the bed is connected to the frame too. When I go over a speed bump it sounds like something is in the bed and goes up in the air and then falls and hits the bed again. I wondering if the bed is loose. Maybe I will crawl under there when I am not feeling lazy.

 

My Ram Sport has about 3/8'' gap from the rubber to the bed. My opinion is that it's only on there for looks, so you don't see a large gap form bed to cab. Personal I'm glad mine doesn't touch because it will eventually ware the paint off, and will do it quicker than you might think, especially with road grime and dirt on it!

 

My old 96 ram had a camper shell on it whose rubber touched the truck. The movement of the truck bed caused the rubber to wear away the paint after about 6 years. I don't think you want the rubber rubbing on your paint.