Any suggestions on a roof mounted cargo box for an access cab?

I'm trying to find a set of roof bars that could be drilled in so a roof box can go on top, but I haven't been able to find either of those things. Would it be better to just get a metal roof rack installed and tie a bin to the top?

 

Generally speaking, you'll want to rethink that idea and maybe go for an in-vehicle solution or one that utilizes the bed.

You don't want to risk getting a leak in your interior.

But really the biggest negatives would be the drastically reduced gas mileage on top of the wind noise said box would introduce.

 

Look at a tower system from Thule /Yakima that clamps your doorframe instead of drilling holes.