PC166 2-2-2... not only hard to find but also likely to be heavily overpriced as end of life products that are still useable in many systems.
I wanted such memory years ago, for my Coppermine 800EB system, which I ran at 166Mhz FSB on a CUSL2. At the time, it did not exist yet. However, I was able to get good Mushkin PC133 Rev2, that ran 158 2-2-2, 5/7t stable, and 166Mhz at more relaxed timings. Mushkin still sells their later developed high speed SDRAM. The 256/stick density means only 1Gb max RAM in your system, but IMHO that should be plenty unless you have some specific urgent to really go overboard and get 2Gb instead, even at much higher cost.
I'd look into such Mushkin-like known 'good' PC133 RAM, instead of focusing on the semi-official "166" label. Timings with 4 (!) sticks are never guaranteed anyway, and I bet that the PC166 you may find will only run at poor timing settings.
Another thing to consider is whether the loss of a couple of latency clocks is a very big deal. It's not perfect, but you're using a VIA chipset anyway.
EDIT: Hmm forgot to talk about the PCI bus. If you've only got a 1/4 divider, the PCI bus *is* a problem at 41.5Mhz. There is not only the IDE system to worry about, but also all the PCI cards... NIC, sound etc. Without testing it's very fuzzy what will run and what will not. In my experience, the PCI bus @ 166Mhz FSB caused the most problems... make sure you know what will actually run and what not beforehand, or you'll be stuck at much lower FSB speeds sooner than you'd wanted.