I really like mine got two one in the box form my next 542 and one that came with this JWD 452.
First yo put them on with no lower dowel pins and get gear clearance right drill to 5/16 and install 5'16 dowels and that is done.
Trick is there are no timing marks!
so you get your degree wheel on at TDC! one of these is the cats butt for this!!
http://chucker54.stores.yahoo.net/crtusowidewh.html
you turn the cam to .050 lift and turn the crank to the @.050 number you desire and then line the top gear up so 7 bolts line up perfectly and tighten gear then do your regular degree checks to make sure where you are!! the mark things and any advancing and retarding of cam from where you are is done buy lining numbers up to the original 1 mark!!

So if you have a 260 @ .050 cam and you want it at 106 you devide 260 by 2 = 130 then you subtract 106 this leave 24 so you want @.050 lift at 24 BTDC (before)