I think you can swap in an escort motor (1.8 or 1.9.. I can't recall) or it was a mazda 323 turbo motor... it's been a while. Research it though..
I wonder if a MX-6 turbo motor would fit...

I've also heard of someone using a festiva as a autocross car (yes, people made fun of them but they did it anyways) I'll see if I can find the videos. I used to have a video of him racing it a few years ago.
I thought those cars were such pieces... until I saw a Yugo... so as long as you can make it fast I'd like to see it. Motors will swap into it atleast.