When I made a Vulcan stock, I made two tools to make the front stock holes:
The first tool was a cut off screw with a sharp end that could be used to mark the hole location on the inside of the stock. With the hole location marked, I drilled the hole undersize from the inside, and played around with round neede files until I got the hole angle approximately correct and was able to enter the screws.
The I made a too to countersink the screw heads, which was a screwdriver shaft with a home made cutter on the shaft. I turned up a steel cutter in the lathe that went over the screwdriver shaft, and fixed it with a grub screw from the side. The cutting grooves were cut with a dremel too.