Cosmo, can you tell me which parts you found weren't interchangeable? I am eager to learn.
Guapoman, I apologize, I didn't mean to sound like I wasn't believing you, the parts you described are sub-components of larger assemblies. It is pretty common for parts like those to have some differences between Toyota's suppliers. The plans is for the whole sub-assy to be replaced as a unit, so that those smaller parts differences wouldn't cause trouble.
Sometimes, swapping out the whole thing is more work, on an old car, so it is tried to break it down into the component parts to change, say, just the button in a HVAC control assy, and in that case this is the result.
As it turns out, I've worked in Toyota engineering for 30 years (just passed my anniversary this week!). Interchangeability of the parts between plants and suppliers is a mantra drilled into us. So, I was surprised to hear it said they weren't, and am interested to learn more about what was found.
Note that the origin of Toyota local manufacture in the '80s (Gen 2 Camry) was heavily influenced by the NUMMI / GM connection, so that a lot of local suppliers, at first, were from GM (Delco, and so on). Over the Gen 3 and then Gen4 Camry eras, that shifted as most of the local suppliers dropped out due to difficulty meeting quality and cost targets, and when new ones were brought in, the standardization of design tended to become easier to implement.
This year I am restoring my rusted out '93 Camry, built in TMMK, using a '92 Camry from Tsutsumi, JPN for parts. So far I've found every component to be completely interchangeable (including one strange detail of the engine wire harness which I thought was a mistake on the first one, but the second was exactly the same in spite of the harness definitely coming from a different source).
Except for the alternator difference that you'd pointed out (even the wire harness connector is different, probably to prevent mixing them up at the plant). That one surprised me when I ran across it myself, too.
Usually, parts are made purposefully different to avoid mix up ("Poka-Yoke")
Norm