look you "NEED" to mark the blades and shaft as they are balanced.. Alot of people claim that te balancing is overkill, but its done by the manufacturer so there must be benifits.. so why not keep tis in balance..

Garrett balances there units by grinding weight off the nut.. this grinded nut can be a btch to get off as well and has to go back in the same position.. this is why i bought a new core for $125 instead of doing a rebuild at $75.. the core is new and balanced, ready to go with your old cleaned up housings.. I got mine on ebay and i could find the email for you if you like.. It was a regular turbo parts supplier i forget the name offhand.