You should wait on doing your drilling (of the metal tabs) for pinning until just after the stock is dyed, or even finished. Those holes need to be cleaned up from varnish that gets in there after the gun is finished anyway. The reason for this is the stock dimensions are going to swell slightly during all your whiskerings and other applications of wetting agents (water, stain, finish) and the holes might not line up perfectly when you're doing your final assembly. If you do it before this you might wind up with a TG that the pins won't go through (too tight) or the TG sits too high to the stock (too loose). Go ahead and drill the holes for the wood, but leave the metal tab till later
Tip; Don't try to drill through the metal tab all the way while the tabs are in the stock, especially if it's a brass TG. Brass is a particularly "grabby" metal for drill bits and can easily break off a bit inside the stock. Then you're in a world of trouble. The hardened tool steel of drill bits is just about impossible to drill out with another bit. Just stick your bit in there to START the hole and mark it, and then remove the TG and drill it completely through on your drill press.