Here is a professional tool for drilling the front and rear trunnion holes in AK47 receivers.
This tool will work with 7.62 and 5.45 trunnions using two different expanding mandrels that fit into the trunnion. The red mandrel fits the 7.62 and the blue fits the 5.45. The tool now comes with both the red 7.62 and blue 5.45 mandrels and the green MAK90 mandrel is an option.
Any rear trunnion can be mounted to be drilled so you aren't limited to just one style.
The one meg worth of photo instructions for using this tool can be found on this page.