One more thing to note is that bearings come in varying grades. In this case, a lower number is a better quality. I suspect the bearings in use in my Pie are greater than 25, because they get really inexpensive at 25 or larger. Anyway, when you talk to your bearing supplier, ask him about grade vs. cost. You may not want to pay for a grade 3, but a grade 5 or 10 might be a reasonable cost adder, and will definitely give you more lifetime. As Alan recommended, polymer seals are usually better than metal shields.
When you consider the added cost of better bearings, ask yourself "Do I ever want to have to do this again?"
By the way, GM isn't the only firm to spec bearings by cost. Colin Chapman, of Lotus fame, routinely used the cheapest bearings he could find. But I sure did love the cars, and even though I'm sure I eventually replaced every bearing in my Series 4 Elan, I'd do it again in a minute.
TTFN,
Dennis