Do you have a hose schematic for a 69 RS? If not acquire one before starting.
Vacuum leaks are crazy and seeing as you probably have original hoses, you probably some with splits and cracks, plus if you have not replaced the vacuum control valve you probably will need to find one... you can bend the tabs and put the new plastic valve on the old mounting plate so it doesn't look out of place on a survivor.
They are easiest to trouble shoot if you can create a vacuum source which does not require the engine to be running so you can hear leaks.
Here is the one I did replacing the valve on the original mounting plate.