Your list looks good, but if you do more reading in the high performance section you may want to reconsider a few of those purchases...
SBP expansion chamber... Buy it, it's the best pre made one out there and easiest to install... only minor mods required, if any at all.
HP Walbro carb kit... Be careful here... The carb is great once installed and tuned right.. the kit is incomplete and will leave you in a lot of headaches... Read about this in the HP section, lots of good info on what to buy to save you a little money and headache
RSE Reed Valve kit... Good kit, not much wrong here, but the reed is pretty small and if you want big power or RPM, there's a better one out there... http://www.arrowmotorizedcycles.com/...block-kit.html
They also have a really bad a$$ expansion chamber pipe, but mods and a phone call required.
Jaguar CDI... You don't want to lose power? do ya? ... The HD Lightning is the best out there and won't hurt your engine a bit, not to mention the stock unit makes great power as well.
diamond Head... Good stuff here... same for the fred Head, or a Puch Hi Hi head if you wanna save some bucks... any of these 3 will make good power and keep your engine nice and cool.
Talk to Fred from CRMachine.com about the ported cylinder or motorBicycleRacing in here if you want some serious performance, or read up and port your own, stock cylinders are cheap so if ya mess up, it's only $25 for a new one to try again.
For the sprocket... if you like acceleration and climbing power, keep the 44, if you like speed but can sacrifice acceleration, the 36 works good, and a 40 tooth is a nice happy medium, I recommend all 3 so you can tune it to your needs and terrain.
Also, for the engine, start out with a DAX engine or get one from MotorbicycleRacing, both are excellent base engines and the quality difference is night and day compared to the ebay specials.