proper idle

i have been doing a lot of reading here and i have still run into some setting my timing problems. 1961, 235. i have looked many many times and have failed to locate the "ball" used to set the timing. what i have found is the upside-down triangle. i marked that and when trying to set that to the needle i may get 3-5 light clicks where it is pretty close, but it bounces erratically and some times the mark doesn't show up. at idle the truck runs fine and then occasionally will "bog down" for a stroke or 2 then come right back up and be fine for a 20-40 sec.

most recent work i did was pulled out the distributor to replace my vacuum advance. since i dropped the dizzy back in i am getting the oil pressure light on. i know i should do the valves first, but the truck ran really well when i first got it less than 100 miles ago, and that is something i have yet to ever do and am waiting until i can get some quality help. just trying to keep it drivable. my concern is it sounds like it may quit running when it bogs down. a lot of info in here and may not be enough to get some good help, but looking for any ideas to clean up the timing issue.

It's been many years since I've worked on a 235, but you might consider some of these topics to get closer to a solution:

1. Was the erratic idle present before the distributor repair, or could it be the distributor might have been reinstalled a tooth off, or 180 degrees out.
2. Can you not find the ball with the timing light, or not at all when examining with a drop light. If it's just not there, perhaps the manufacturer changed the mark. If it is there, but doesn't show up with the timing light, it's likely the distributor is installed incorrectly.
3. Make sure the timing is set with the vacuum advance hose disconnected from the distributor, and plugged. If the line is left connected, it can alter the timing. If it's left disconnected and not plugged, it can raise the idle speed enough to introduce centrifugal timing.
4. Make sure the weights and contact areas in the distributor are clean and lightly lubricated. If they stick it can cause erratic timing.
5. Make sure the points are set correctly before setting the timing. Changes in the dwell alters the timing, so always set the points first. If you have one available, set the points with a dwell meter rather than solely with a feeler gauge, it provides a more accurate result.
6. If you have access to an ohm meter check the condition of the plug wires, including the coil wire. If they are old, tired, have turned to wood or have visible cracks, they could be leaking enough to cause erractic ignition.
7. Check the condition and gap of the spark plugs. If they are fouled, Google a search on reading spark plugs to further diagnose.
8. Check the distributor cap for carbon tracking or cracks, and the points for pitting. Tired points can cause numerous hard to trace headaches.

That's about all I can think of without knowing more about the existing and previous condition.