Hmm, that's an interesting discovery! If the original flash chip was a 5V chip I have no idea how it even worked. I guess it's possible that they added level shifting between the 5V flash chip and the 3.3V Sil3112 chip, but I find that unlikely...I would think it would be far easier for them to just use a 3.3V chip. If you want to check what the card wants for sure, I would put the card into a system, power it on, and measure the voltage on the VCC pin of the flash chip (pin 32, the one just to the right of the dot marking pin 1).