really we need more info for a recommendation. You need to provide what type of riding you plan to do and what type of mods you are planning for your engine. I would not change the carb for a stock bore w/o porting w/ just a pipe and open airbox.
He has another thread that ties into this one. Jetting will be affected by the type of mods that have been done or is currently planning for the engine. Riding style can change your jetting as I have friends who run rich on the mains because they spend much of their time riding in the 2/3 to full throttle range (this has been recommended to me by a few builders). The reason for this is to help with cooling, engine life, and to help protect against a seizure. I was also informed by a well respected builder that most people run the Blaster too lean in the middle and he warned me to watchout for this as it can cause seizing problems for people who ride in the mid-range. However, you are right that generally a properly jetted carb will do its job nomatter the rider.
Who made the big bore that is going on it? And unless Keihin has just started making them, they dont have a 34 pwk. 33 and 35 pwk's are most common on blasters. They do have a 38pwk but you rarely see one on a blaster due to it being overkill on 99% of blaster engines.