I am doing a 200tdi conversion - but the Alpine got in the way - apparently the 300tdi is not a big deal to fit either.
If you would like a copy of an article I have written on how I did the conversion, send me an email charlie_myres@yahoo.com.au
Mine has the standard S3 box for now, with overdrive, which is another way to keep the revs down. I plan to fit a New Process gearbox one day,
Cheers Charlie

