The factory timing was not optimum for the stock cam , timing needs to be set where it makes the best power this requires modifing .
I do not have the stock specs handy but with less overlap & more lift & a slight increase in duration , it will run better make better power & milage , I suggest you leave the vacuum advance disconnected , set timing at 36* at 3000 rpm & you should have about 16* at idle , the stock cam design is 40+ years old ,there are better cams available