Now, there are some extra non-dash related things I would probably do since your dash is already out.
1. A heater refresh would be nice. At a bare minimum you could remove all the plastics from the heater and clean those while adding new sealant around the edges. You can go all the way by removing your whole heater box and doing a whole refinish on that as well with a good core flush. Its a big pain to get the heater out with the dash in, so pulling it now would be wise.
2. I would recommend switching radios now. On the '69 there are two brackets that support the dash in the center. Unfortunately they also block the path of the radio from being removed. If you have the dash off, you might as well swap out that radio you want to replace as it will just be impossible once you reinstall the dash.
3. Clean everything! Im sure its the first time your dash has been removed so take some time and clean everything that you can. As you saw above there is some crazy dirt and grime... you have free access to the areas that were once covered, so clean them up.
4. While you have the gauge cluster out, switch over to LEDs. They are cheap and a great upgrade that not only looks nice, but is a good safety feature so that you can actually see your gauges at night.