225 V6 Rebuild - Parts Source?

Yes, I would expect my shop to fit the pistons to the bores. One option is to let your shop choose and purchase the parts - as a business, they can get the parts at cost, and should be able to provide them to you at retail or less. Ask - let them make a little money on the parts sale, and at the same time guarantee that the parts you get will be suitable.

 

I would not be too quick to blame that on the manufacturer. In the trade, lots of parts go out to the customer and come back for some reason or another. Intentional or not, parts get mixed up and sent back, ending up mislabeled. They just go back on the shelf.

Be suspicious of anything like this that does not look pristine and new - no fingerprints, no torn box tabs. Just be aware. It's still up to you to measure and inspect the parts before you install.