sask, I'm not sure what year of truck you're referring to but I imagine the dents are at a 'double skinned' section and you can't gain access from the inside.
As Don said,pics would help,but his suggestions are what I would recommend as well.


1950 Chevy Advance Design 3100 in Scotland
In the Stovebolt Gallery
More pix on Flickr.
I've definately got this truck thing in my blood ... my DNA sequence has torque settings
"Of all the small nations of this earth,perhaps only the ancient Greeks surpass the Scots in their contribution to mankind" Winston Churchill.