Have you tried automatic transmission fluid mixed with acetone? (50-50 mix) I have managed to get out some ugly stuff with that... It is cheap and seems to work better than all the brand name penetrating oils. might be worth a try. Good luck!

 

I had a 97 GMC K2500 Suburban SLT for 11 years. Great truck but I can relate on the front brake issue! Me and a friend heated the hell out of things with a torch until cherry red and that worked. I only did that job once. The next issue with the brakes on that truck drove me insane for awhile. The rear drums kept warping as the result of the combination valve going bad. Basically a proportioning valve. Three days later traded it in on a new F150 Lariat Ecoboost and I love it.