Buddy I'm on the same quest lol as far as I know so far you need
1.8 t block + all ancillaries + loom and ecu
S3 gearbox
S3 front drive shafts
S3 engine mounts
Custom exhaust or maybe s3 might fit if you go straight to k04
Then you need to get it all mapped
I'm sure there is more to it but I've left my project book at work which has everything written down in it