Sure you want G40s for a pubber? I ask because G40s are one of the first grey clinchers that Mavic did and I'm guessing there won't be many around. I understand if you want to build something special, period correct and all that, but it just sounds you want some grey rims for a clunker.
You'll have more luck going for something a bit more common like MA40s or Open Sups or some of the modern replica models stocked by Spa cycles