Well, according to the GM service manual, there are some special tools the dealers use to remove the bushing, using a press. About the best you can do it check to see if you can rent them. Even new control arms come with out the bushings, so it is possible to replace them. Maybe if they are real rusted you will need to use some heat on them too. Instructions from the service manual enclosed below for you. Thanks
Important: Do not transfer bushings from an old control arm to a new control arm.
Important: New control arms do not include bushings. New bushings are available separately.
Sorry, I tried to post pictures of the tools for you, but the file is not the correct type for this site to accept and I have had no luck trying to convert it. According to GM they want you to remove the control arm so you can use the special tools in a press. A fork may work. You will just have to try it and see. The only other thing I could suggest would be to just burn them out. Good luck.