Nice find , enjoy the build .
Does yours have disc brakes ? Power steering ? A/C ?
The C.A.P. Is a good thing , it gives full advance on deceleration and normal vac advance other wise . The result is it gives more time to burn off the rich fuel ratio on deceleration. And Chrysler was able to not add A.I.R for a number of years . Not bad for such a simple device and it saved them millions.
On my ‘73 Dodge van with a mere 300,000 miles I find when cranking it won’t fire until I back off a bit on the key . So I think the switch has served its purpose and time for a new one .
If yours acts like that you now have an answer .