Since the car spent 15 or so years in illinois I have had some issues with rusted bolts, especially lower fender bolts. I'm fairly certain there will be significant issues removing the body bolts. Since I can't spray the threads from underneath and they are covered from the top what do you think about this idea or does anyone have experience with it? My thought is drill a small hole in the floor above the bolt/nut and spray through the hole directly onto it.

 

I think that maybe a good idea, but have you made an attempt to try to remove one of the bolts by using an impact tool? I was able to remove mine using the impact. But I was prepared to cut a hole above the nut if it began to slip.

 

Exactly. Drill access from above, test your lubricant for flammability, heat the bold head from below to something below that flash point, spray into the hole. As the bolt cools, it will wick the lube into the threads. Then apply an impact ... sparingly. In, out, in, out, in, out ... a quarter turn at a time to allow the threads to shed their rust and crap instead of trying to drive it through the threads.