Total timing...

[threewood]

Bring engine to operating temperature.

Unhook vacuum advance and plug vacuum gauge into manifold port on carb.

B/RB rotate distributor clockwise to advance until you get highest vacuum reading.

Adjust Idle down to where it idles around 800 - 1000 rpms.

Re check vacuum. Next adjust the two idle mixture screws for highest, steady rpm.

Re adjust idle. Once you achieve highest RPM, back both in 1/2 turn.

Now check initial timing with timing light. From here you need to make sure your total does not go above 36 degrees. On your advance plate in the distributor should be a number. Times that number x2 and add initial = total. If you have stock distributor springs the all in will come in late. To change mechanical, you need to weld the slots or get an advance plate.

Once total is correct, plug vacuum advance back into the vacuum port and adjust idle down.

 

[Stumper]

I set mine in reverse. Using a dial back timing light, I set the total timing to 35* at about 3000 RPM and let the initial fall where it may. When I checked the initial it was at 12 or 14 (I forget now). I was happy with that and locked the distributor down there.

P.S.
Factory spec's call for TDC. I suspect that was an early form of emission control.

Some performance engines you have to do it in reverse. If you run very light springs on the distributor weights (or no spring) the initial timing is impossible to read. It bounces all over.