@Lucius Helius
Sure

@Salty Oreos may I use this in a mod of my own? I'll link credit here.

No it doesn't touch the blackened tagelmust, and changing the class will affect protection values.
You should try tinkering with the stealth multiplier if you're wanting it to have a stealth bonus.

Does this fix the Blackened Chain Tagelmust to have the stealth modifier? I don't know if simply making it class GEAR_LIGHT is the way to go as I don't know if that will change any other stats.

If you want it in the vendor's inventory specifically then the vendor needs a backpack.
Vendors that run stores won't need the items in their inventory, just in the shop.
If you just want to add to an existing shop, go to the vendor lists section in FCS, and edit the ones you want to change.

hey, I had a mod question. If i was making my own mod, how do I allow items to spawn within a shopkeepers inventory

Cool mod!