Can you upgrade a first gen Mac Pro with a x54xx Xeon?

I took the liberty of purchasing a Xeon x5470, to set the record straight, and legitimately troubleshoot whether or not I could install a Xeon x54xx into this Mac Pro. This video serves the purpose of being recorded proof on my attempts to install a x54xx Xeon into a Mac Pro 1,1. This means, however, I am hinting at getting either an 08 or 09 Mac Pro, in the distant future. The 07 Mac Pro bodes no performance issues, merely, it is that I cannot install Sierra, which bothers me.