I've also been referencing the "Mactracker" app
http://mactracker.ca/
and it seems to go into more detail than other sources, naming these other chip designations "Bloomfield" and "Gulftown" for the MacPro5,1. I'm wondering if those are all covered by the "Westmere" umbrella.
The other issue is that Mactracker doesn't mention "Nehalem" for the 5,1, whereas EveryMac does. The machine I'm looking at is a Quad-Core 3.2, which EveryMac says is a Nehalem.