He never mentioned who he bought them from, sounds like they are used carbs from someone else. The CPW carbs are keihin bodies without the pwk casting on them.
Yep pick your tire based on your motor, type of riding. Im going to say you wont need a tallter hauler. More than likely a 8 or 9 will be what you need.
From what I have seen the balls work really well, make sure all the parts are cleaned really well before you start polishing carb cleaner and wiping down with a rag works really well.
A good way to go about building the 350 the way you want is to look at some components on some crate motors and copy what they have used. Putting a big block in is a waste IMO why add the extra weight when you dont need to.
All depends on what you want to spend, this is about what a 4mil setup whill run from anywhere. http://cgi.ebay.com/ebaymotors/Yamaha-Bans...98699QQtcZphoto