First step should be ordering new bolt(s) to replace those since you will destroy it(them).
Next, get a torch and some penetrating spray like PB Blaster. Spay the knuckle as much as possible where the bolt goes through. Use the torch to help the penetrating spray further "penetrate". Remember that the penetrating spray will go toward the heat.
Are you replacing bolt lateral links? You might have to because the torch will probably fry the bushings.
Once you think you have enough penetrating oil, try to turn the bolt. An impact gun would be worth its weight in gold here. If it doesn't, more heat and penetrating oil. If that doesn't work and you don't have an impact gun, use a 3 lb sledge hammer to pound the bolt out (this is where you destroy the bolt).
While removing a similar bolt from the rear suspension of my Saturn, I ran into this same problem. Many hours later of torching, pounding and cussing, I finally got the bolts out.
Good luck. Keep us posted on how it goes for you.