speedo gears

50 and reading 46 , so the speedometer is reading about 8% low. You just need a gear 8% smaller to speed up the speedometer. So take whatever gear you have and reduce it by 8%... 36 tooth ÷ 1.08 = 33 tooth, 34 tooth ÷ 1.08 = 31 tooth, etc...
There is nothing wrong with the charts either. But if you really know you are reading 8% low my way will work too.