I can't be entirely sure of how they'd hold up. The 3A-C engines (A family being the predecessor to the ZZ family) use aluminum bearings and have excellent longevity.
http://www.enginebuildermag.com/2012/10 ... -bearings/ Here's an article. It mentions that aluminum bi-metal (aluminum with steel backing) bearings are used most frequently on modern engines and are excellent for low-load engines, which the 1ZZ can probably be safely classified as.
As far as the different sizes go, you have much greater tolerances accepted in an overhaul than what Toyota allows in their factories. You are allowed 0.028-0.080 mm clearance, via service manual. Toyota wants as close to a guarantee as possible that your car will be exactly like the experience they want you to have (basically, perfect), so that's why the sizes vary by 0.007 mm and not 0.25 mm. If you can't fall within the range in the service manual, you will need to have the crank refinished to 0.25 or 0.50 mm undersize and to get the matching bearings, then measure to verify.
Make sure you get everything really clean before you put that puppy back together, and measure the clearance. You may also need new rod bolts for it, I think they are also intended to stretch (stretching has more consistent clamping force) and after stretching, no longer clamp as well.
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