You should use a thread from the 30's to have it 100% right.
You will find that easyly in Great-Grandma's sewing basket.
Or on fleamarkets, on ebay.com or ebay.de for a real cheap price.
So afterwards there will be nothing that will not stand the "black light glow test".
Fakers overlook that little details sometimes when pimping an item.
Do not rush the whole thing. It should be done with great consideration.
You may want to have the item around for years, don't you.
So it might take a few months to have it perfectly restored.