What you need is an internal bearing puller. You'll have to do some leg work though because they're not that easy to find. It's basically the same as the anchor bolt idea but a proper kit will come with a fitting that hooks on the inside edge of the bearing and a slide hammer that threads on to that. Good luck, I've been there!
Question, how hard do the new bushings go in? I have an '82 that I plan to go to a PAMCO on....I was able to pull the advance setup out of an old head (one with the labirinth bushings) and tried to pull the bushings out just to see if I could...kinda tried half hearted, but it seemed to install them in mine I'd have to put them in the freezer or something????
Can the bushings be installed without pulling the cams?