Timing Belt

I was wondering if, on any car, it is possible to exchange a timing belt with a timing chain. I know it's a long shot, but I don't see any reason why one wouldn't be able to do this with some time and patience. My Porsche is about due for a belt change and since I do all my own work, and I couldn't find anything anywhere on exchanging belts for chains, I figured that I would ask if it is even possible. Thanks!