Guys.... it is not possible, for all practical purposes. There might be some strange rare and risky approach of unsoldering a chip and soldering in a new chip..... and ruin your motherboard.
If you have a Version 1 motherboard with the earlier boot block date then just max that out and be happy, with 1 or 2 processors that were the fastest for that era.
If you must have a Version 2 motherboard you can find those used off eBay and take a day and swap it in to your original box, and upgrade processors.
My advice is this: Find a single processor Z600 Version 2 workstation on eBay that is running the dog-slow lowest performing processor and buy it cheap. Then, get two of the fastest (or better yet, next to the fastest if budget is limited) used processors off eBay. Get 6x2GB sticks (or if you really, truly, need it 6x4GB sticks) of memory, and a good used Intel 320 series 300GB SSD and build up a W7Pro64 box.
You will be very happy......