What causes "dieseling"

Principally, as has been said; as to engine run-on, this is caused by
the throttle blades being too far open, at engine shut-down.
This allows the inertia of the spinning crank to allow the atmosphere to keep on bullying it's way into the engine, past the throttle blades, where it picks up fuel;
and to continue into the chambers, where, anything glowing-hot can ignite it, including hot sparkplugs.

BTW-1
You can idle that engine at any rpm you want to. That sticker provides the baseline to pass emissions in the year it was manufactured. It has nothing to do with best performance, nor with best fuel-economy, nor with best anything.
Nor is the engine, with stock timing and carburetion, going to be the best that it can ever be; no matter how you set it.
But
those factory parts can be modified, to get reasonably close.

as to fueling;
most of those emission carbs have what is commonly called, a "throttle-kicker"; which is like an electric fast-idle device. When everything is working right, you probably will never know it's there.
It's job is to reduce the idle rpm to near stalling, as soon as you shut the key off.
It is called a kicker, cuz as soon as the engine runs, it kicks the idle UP, to prevent that stalling.
What this means to you is that if you have a kicker, you now have TWO idle-speeds to set; the first is the base throttle opening, aka the curb-idle speed, and the second is the running idle speed, with the kicker engaged.
The first is set with the curb-idle screw, to just above stalling, and the second is set by turning the plunger shaft, that is sticking out of the kicker, but before you do that,
1) verify that the kicker still works and
2) those kickers rarely have enough power to actually kick the throttle open, so you gotta open the throttle just a crack, manually, and then you can work that shaft, which usually has a hex head.
3) That said; if you change the timing AFTER these two idles have been set, you will need to reset the idles again. So do the timing thing FIRST.

As to ignition timing;
Every internal combustion gasoline engine, installed in a passenger car, has FOUR basic timing requirements. In order of importance, IMO, they are;
1) maximum Power-Timing
2) Power-timing at stall-speed, for automatics, obviously
3) Cruize-Timing
4) Idle-Timing

As to Power-Timing;
ALMOST all SBMs will want at least 34 degrees of Power Timing, which is the total of;
1) the max that the distributor can supply, added to,
2) whatever you set the IDLE-Timing to.
However, different configurations of engines will determine how soon or how late, this Power-Timing number will be accepted by the engine. Some engines will not detonate at 36* at 3800, but will detonate at 3600. Some will accept 36* at 3000. More is not necessarily better.
A reasonably safe target number is 34* at 3400rpm.
You will need a tachometer and a timing light. If your balancer is not scribed out to some 40 degrees, then you will need a Dial-type of timing light. Alternatively you can install a Timing-Tape on your clean balancer, and use a regular timing light.

If yur not into modifying distributors, do this.
1) With the vacuum advance disconnected; check and record your current idle timing
2) rev the engine up until the distributor stops advancing. Record the amount of advance, and the rpm at which this occurs.
3) subtract the little number from the bigger number. This is the amount of advance that this particular distributor is "programmed" to supply. This is usually called the Mechanical Advance.
4) Whatever the number is, subtract it from 34 and set your Idle Timing to that smaller number.
Example, if you get 24* of Mechanical advance then;
34 less 24 equals 10, so set your idle timing to 10 degrees.
Then go tune your curb-idle, down to just above stall. Then set your running idle rpm. then tune your mixture screws to best lean idle. Then
Hook your Vcan back up, and roadtest it.
As to Cruize-timing,
If yur not into taking apart and modifying the guts of your distributor, just drive it, as above. Just know that there may be gains to be had, in those modifications, but the realization of those gains can be a lotta lotta work.
Just drive it.
As to Idle-Timing
Again, to change it, after the Power-Timing has been discovered and set, requires the distributor to be disassembled and modified, and honestly your particular engine hardly cares what the Idle timing is, just set the power timing, and drive it.
As to stall-timing
In your application, the first time the engine really cares about timing, will be at Convertor stall-rpm; and one more time, you cannot easily change that ............ just drive it....... unless she gets into detonation,
now you gotta make wholesale distributor changes.