Or google the late "Hagar transfer pressure smileage"
No, the holes in the "out" banjo bolt are tiny, which won't give you an accurate reading of the internal pump pressure unless you drill and tap the end of the bolt, which is directly connected to the internal pressure of the pump. If you're hesitant to modify the bolt itself, you could (assuming you have access to some basic tools) make a new, custom stand-off which has a fitting for a pressure line to a gauge using stuff that should be readily available at a good hardware store. That's probably what I'll end up doing when I get around to checking my IP pressure.