Yeah, this has been gone over here a number of times for different models.
A Search will get you what you want to know.
Guys with the SOHC Fours have the same problems, as they all use the same steering bearings, more or less. That's all documented over at http://forums.sohc4.net/index.php
. That's a very large site, do a search there and you'll get a ton of info.
From personal experience, I think Pyramid stuff can be iffy in fitment sometimes.
The AllBallz kits seem to give less trouble.
I put Pyramids on my 450 and had to grind the stem a bit to get the lower race to go on.
Like Steve said, worry about getting the bottom worked out - you may need the washer to keep the bottom clamp from rubbing on the neck.
The top will work itself out, most likely, try it and see.......