You also have to install the gear shift and links. If you can get all the bits off some kind of 3S-GE FWD front cut then the job might be easier.
As far as just swapping heads, unfortunately the S series engines aren't the same as the A series. The oil galleries are different. The way the cams are run is different. I lot of things are different. I think there is an article on the web able the technical difference between the 3S-FE and 3S-GE.