This is the site where I got my information, he has a guide on there but its for a 5:1 ratio. I emailed him for the information and got the specs for a 4:1. There is absolutely no reason you could not get your parts from here, I was just lazy and when he linked me to a site I just bought from them.
http://www.micro-heli.co.uk/
He also has a video on his site so you can hear how non crunchy it is. The only thing I have to do now is fabricate a spacer for additional clearance on the cover as the pulleys stick out futher. A project for the weekend I think.