You can fix the problem with the flat spot and the rough idle by soldering up the hole in the base butterfly of your pic 3, or so i read on this very interesting site " Rob and Daves air cooled pages" however i opted to try and keep what is supposed to be there, there. this way i keep the correct timming degrees etc for the engine. the unit I used in my dizzy was a no brand I got from wolfsberg west for about $45 when he was at the SA day of the VW. very easy to fit, then stripped and cleaned the carby, tuned the carby as per the instuctions on the same web site Rob and Daves and the old girl has never run better. Only need to replace spark plug leads now as i still have a liittle miss when you take the revs up whilst sitting still ,minor but i might as well get it spot on. check out the pages as I said some good reading here is a link
http://www.vw-resource.com/index.html cheers
RJ