I'm not sure why you would want a bigger engine as the factory engine can easily make over 200 wheel horsepower with the right modifications and run reliably. The only two larger options require significant effort for installation and cost. The most common displacement upgrade is the 5EFHE. Its a 1500cc engine normally found in the Paseo and other Toyotas. To get it to work you must hybrid it with the 4EFTE. There are several guides on this site. The hardest option is the 4AGE20v. This is a 1600cc engine that can be made to fit with lots of work.