Hi, new to the forums and working on cars in general. Have to replace the heater core on my 90 lx 2.3 mustang. Step one I hear is to remove the seats. I've been stuck for 3 days trying to get the 2 rear bolts for the front seats to budge. I've used wd40, open and shut spray, box end wrench, ratchet, electric impact, it won't budge. I'm a novice, any advice would be greatly appreciated.