a 4ac hasent got the grunt of a 4age. the difference is 4age is twin cam(the proper style) and obviously efi. 4ac is just sohc. look for them in ae71 model corollas (the last rear wheel drive model after yours) or even drop a fwd one from a ae82 or something in it. these engines have more power over the k's and are also very easy to get power. fit a 32/36 weber, extractors, 2 inch exhaust, give it a cam regrind, while your at it shave the head and port/polish. also try to get the electronic dizzy model.
i did most of this to the 4ac in my ae71 wagon and it went f^&kin hard. you will still need to change cross members etc as it is still a "A" family engine.
hope that helped :)