Hi, usualy the belt needs to be replaced when badly faded or after any collision when used.

I have had a set like yours... The badly faded belts are ruff and not as flexable.

I use to have a link for a reputable seat belt company that has various weaves and colors. They are specialist by trade and all they need is the heads and lables if doing a full restoration. But since your doing AMC you may just send them the belt for an exact duplicate to be matched.

When I have time I'll add the link here... They may no longer be in buisness, since I have not used them since the early 90's.