machining hub for key

Since I have an extra hub sitting around I want to get it machined for a key.. my crank is a stock GM crank. I figured I'd save the shipping hassle of returning the core and get it machined locally. Does anyone know the dimensions or anything else I should tell the machine shop (assuming I find one) when asking them to machine the hub for a key? Also where can I get a key for the hub?

I just bought one from thunder racing and put it on or I could tell you everything about it. I do remember that if you put a smallbock key in you crank and measure whats sticking out that would tell you how deep to go. Make sure that were they cut it is about the 2 o'clock postion compared to the TDC mark on the hub. It may be hard to find a machine shop that can do that because you have to have a special bit because of the hole being blind. Good luck