I normally just get a 520/120 link and use my dremel to make my chain its the easiest way in my mind..
some post have led to concern of lower chain block wear with the 52 rear and the 12 in the front certainly wont help the front chain glide (you may want to check the lower front of the swing arm chain glide) here is a link to replacement chain glides
http://www.hotfootmoto.com/Site_2/Kawasaki_Sliders.html
what is the reason for such radical gearing..? is your bike running right?
..I was happy at 13/50 then went to 14/48 and settled at 13/48.
I just think you are going to be shifting alot and spinning your tire.