Up 3 teeth in the back and down 1 tooth in the front is usually the norm. I dont usually mess w/the stock set up. Its a pain getting your speedo set up right and highway driving adds almost a grand to your tach.
speedos are usualy off about 5% from the factory anyways. so a speedo healer would fix the problem with or with out changing the sprockets. i have a 2005 636 and i went down one in front and 2 up in rear and added a speedo healer and now my speedo is dead on and odometer reads perfect. and like he said it will add rpm, i do run about 8000 rpm doing 75 mph.