Thanks James, With what you've seen on all the original gauge cars, and what I've read here, I'm confident we are on to something.
Unfortunately it doesn't sound like American Autowire is able to help either. Here is the response I got this morning.
-------------------------------------------------
Good morning Larry,
I pulled one each of our CA97542 and CA95266 harnesses from the shelf (and took a look at the GM prints) to check into this for you. The wires you mention in your harness do not have any type of cloth covering on our harness, and I do not see any mention of the covering on the GM blueprint. This could mean there was a change to the harness during its service life, but I can say I'm not aware of any harnesses we manufacture that would include that type of cloth wrapping.
The resistance wire used in a points ignition harness does have a cloth look, but does not have a covering on our harness or in the print. The water temperature sender wire will use what we call "asphalt sleeving" in our catalog. This would be the closest to the covering in your photos, but is black in color.
We'd have the asphalt loom available to sell by the foot, but no type of sleeving as shown in your photos available. Sorry it's not an easier answer on this one...as mentioned my suspicion is this would have been a revision at some point in the production run.
---------------------------------------------------
So it appears they can't even put cloth on the wiring even if requested. Sounds like you get what you get and that's it.
So what I'm going to do at this point is forget buying the engine harness, keep what I have even though the cloth on mine is ratty, it's at least original and has merit to the cars original gauge package. I'll buy a new light harness that has the charging system wiring as it appears there isn't any special coverings on that harness (other than the temp sender but they are duplicating that)
So for those looking to duplicate a factory gauge car engine harness, it doesn't appear anyone has a "correct" harness but rather a generic version. If someone can find a source of the white cloth covering that may be the only route to take. I have yet to find any in my searches.