I had a real run around the first time I bought a new alt ( <hangs head, kicks at ground> I was in a hurry!) at C-Tire, as it wouldn't line up. Like a bit more than a quarter inch. Pretty visible just from looking. Checked all their other ones in stock too. This was after I tried the alt off my A/C equipped parts car, as well. Even ran it, tensioned with a cargo strap, for a short while. I couldn't afford the downtime.
Short version. I had to play swapsies and ended up with a machined steel pulley that may or may not be the 'correct' one, but it lines up, that came of a wrecker yard Bosch alt. I've built a couple franken-alts since, swapping wrecking yard alt parts onto proper housings and reassembling them, and this pulley and washer combo has migrated across, and the 'new' pulley gets fired under the bench or put onto the donor alt for use as core charge filler.
Good luck! I suspect some rebuilders catalog somewhere printed the wrong offsets and they've been running with that since. Minor PITA.
Cheers
Trev