The Lenovo version is visually very similar, aside from the Lenovo logo.
Unfortunately you will not be able to upgrade the old CPU to a brand new model, even if you can find a model where the CPU is not soldered to the motherboard, the CPU socket will still be out of date, meaning it will be impossible to put a modern chip in it.
You *may* be able to put a solid state drive in the older machine, but to be honest it's not worth spending the money.
Lenovo purchased IBMs PC division in 2005, so any machine produced post-2005 is a Lenovo machine. Lenovo also used IBM branding for a further 3 years, so despite the machine saying "IBM" on the case in 2008, it was in fact still Lenovo.
Even before Lenovo's takeover in 2005, IBM were no longer making their own machines, in 2004 a Chinese company was producing the IBM ThinkPads "FOR" IBM.
To summarise, if you want a original quality IBM ThinkPad, you'll have to go back more than 10 years, to a machine with at best a "Pentium M" chip.
Possibly better to go for the "chinese imitation" and uninstall the spyware.
Hope this helps.
-J
Do you mean to say upgrading to pentium duo would be impossible and therefore getting 64 bit is also impossible?