"71 Tradewind LY speaker wire location

[Wooden Rivet]

I need to install speakers for a stereo/cd player. The wire harness and the antenna are accessible in the control panel, so I assume it has been wired for speakers. I have the "72 service manual that gives the speaker location, but would feel much better if someone could confirm the location before I start chopping holes in the interior skin. Location given: 12" front of first rib/ up 47". Rear speakers 162" aft of first rib/ up 50". I have a '71 25' LY twin. Thank you for your efforts on my behalf.