Suzuki Swift 1991 engine conversion

Im looking to buy a suzuki swift gti. However, Its very hard to find a gti these days with a low mileage; so I've decided to buy a swift and just put a whole new engine in it. (something fast, with a low mileage.) The problem is I'm not very good with these things, so any advice about what engines would be a good fit etc would really help me. Thanks, Nozy x