Hitch Installation
 

I have a 2004 Chevy Trailblazer on which I want to install a Drawtite hitch. It should be an easy installation, but I cannot get the existing bolts out. There are two on the right and two on the left which go through the frame. I was able to get the nuts off, but the bolts will not budge. I've hit them with GB Blaster, but nothing. They appear to be loose as I can wiggle them with my hand but they will not back out. The bolt's heads appear to be connected with a metal strap/bar. Anyone else have this problem, and, if so, what was your remedy?
Thanks in advance!