The Prius rims didn't work out. Although it was close, they didn't quite go over the hubs, and I'm not interested in having them machined. The scrapyard does have a set of 3 (not 4 =() Civic HX rims that I'm considering making them an offer for, but that's realistically a project for next year. I'd want to find a lone HX rim to complete the set with before buying an incomplete set. So, I ended up getting a set of Nokian Nordman 5's mounted on my stock rims.
It's hard to estimate the impact of winter tires on my gas mileage. Right now I'm getting anywhere from 70 to 90mpg on the straightaways I was getting ~100mpg on at the same 50mph with RE92's in warm, dry weather, but the weather is not comparable. Plus, the tires are not broken in yet. The handling is certainly different, though. Taking corners quickly, there's a bit of a "rubber band" feeling that wasn't there with the Potenzas. The Nordmans are also considerably more whiney even at low speeds, but even with 47PSI (max sidewall) they have a significantly softer ride.
Today I cleaned up the rear drums and rims, which were showing a lot of corrosion where the different metals were in contact with each other.
Before:
After, with a coating of anti-sieze to hopefully minimize further corrosion:
At first I thought the rims were badly pitted, but after going at it with a razor blade for a while, it looks like there's some pitting, but mostly there was corrosion built up on it. It might just be in my head, but I'm thinking the wheels might be slightly quieter now. Maybe they're sitting more level?