No way to do it in the "Vanilla" version, huh?
I'm well into a playthrough...I am not great with Modding, but adding this Mod would probably "break" my current game wouldn't it?
No, its not possible in "vanilla" Fallout1. You must use either separate mod for this called NPC MOD or multi-mod pack like "FIXT". I can't recommend you FIXT, it made me angry after several problems with stability and game hanging when saving. I plan to try with separate NPC mod/
You woould have to start new game in order to use this mod and allow your companions use armors.
good luck :)