Probably just age has taken it's course, get some 400 grit and go around the edge till you see some tiny little marks pop up 5-0-10-20-30. While your at it verify that TDC for #1 = 0 on the balancer. Otherwise you'll be pulling hair messing with the dizzy for nada.
Just a note...this "should have" been done prior to carb tuning or is this oart of the results.

My preference:
1. Pull all the plugs "NOWS A GOOD TIME TO VERIFY TDC = 0" and read for service reasons, (ok) clean/check gap/install
2. Check rotor/cap/wires - wear, carbon track, cracks"poor gas in the cap" service as needed.
3. Check carb for leaky acc pump, general function.. fix what needs it.
4. Start engine alow to warm to normal opp temp, check idle speed - if correct pull the dizzy vac and check for vaccuum should be none. If the idle speed is correct and there is vacuum check the timing, no vacuum check it anyway. You may go back and forth a bit with timing/idle speed if timing was off.
5. Correct timing, idle speed complete cover vac hose and rev motor to check that mechanical advance is working(smoothy) connect hose and check vac advance works. "Might wanna use search and read up on this part" or ask plenty of questions this seems to have a huge argument as to how to whats too much etc... And I dunno for sure, I try to leave well enough alone.
6. Finally connect the vac guage and adjust idle mixture, you may be adjusting idle speed again as well depends... Irractic readings at this point are likely a vac leak/valve train issues... It's early surely Ive overlooked something...cant wait to hear what it was..