You remember correctly. It's actually 5 holes, but two of them are tiny. Two outer holes, 3/8 in diameter, two additional anti-rotation holes, about 1/8 in diameter, and a single center hole for the lamp.
You can see them all (sort of...) in the OP's picture. I highlighted them in red.
I am kind of surprised at how many fully painted dashes I end up welding on after they are painted. I actually bought a super nice dash at the last Wild Horses Swap Meet that I inspected for a good 5 minutes in the glorious Lodi sunshine. Got it home, stripped it, and started prepping it for paint before I realized that there was an additional gauge hole that was 2-5/8 in diameter next to the ash tray. I have no clue how I missed it. So I can't say anything bad about a couple of extra holes anymore.
Eventually the OP will end up welding up that giant rectangular hole. It is up so high that any 70's AM radio will interfere with the defrost hoses. Then he will be back to normal, and can either get that nice RetroSound unit from Wild H...or cut a new DIN mount.
