Quick update. The first couple of uses, I managed to pop one of the belts off of the pulleys when hitting heavy grass, or lightly scalping the ground. I noticed that the two belts were obviously different ages, so the tension wasn't matched...having the loose belt correctly tensioned made the newer belt too tight (bad for the bearings).
So, I got the Goodyear belts from Amazon....$11 each! They fit perfectly, and they aren't popping off the pulleys like the older, incorrect belts were, and I intentionally ran it through some heavy stuff to test it...no problems. The bad news is I just posted a review on Amazon, and noted they increased the price to $25 per belt. I got the last two in stock, so it's likely they were from an earlier purchase, and the prices have gone up. Still, their price is something like $9 cheaper than the next best, and I'm happy they're Goodyear belts made in the USA!