That's an EASY ONE to answer!
Evloution.
They stared with a base distributor, and EVOLVED to have centrifugal advance, then vacuum advance,
When the breaker points were removed and electronic trigger installed, the switching transistors of the day couldn't handle the full 12 volt at full current load.
Now we have transistors that WILL handle full current switching load,
BUT,
When something is a 'Direct Factory Replacement' it has to be built to the specifications of the original part (Mostly to pass emissions, and be labeled as a 'Direct Replacement').
Now we have ignitions that will do MUCH BETTER than factory, but if they aren't 'CARB' approved, they can't be used in emissions states.
(Or at least can't be obvious when the 'Visual' inspection is done)
Remember, these are 28+ year old vehicles... And the government hasn't kept up with the times/improvements down through the years.
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Now, the cheapest 'Upgrade' for a module is the 'John Strenk Stealth HEI upgrade',
You simply pry the guts out of the existing module,
Use the case for a 'Heat Sink'
(High current switching creates a lot of heat, so you have to dissipate that heat to keep the module alive)...
The factory HEI distriubtor housing is made of aluminum, and a lot of it, so GM used the distributor housing as the 'Heat Sink',
While in the conversion, you need to supply a reasonable heat sink.
The factory case works pretty well and conceals the module switch at the same time.
You simply pry the guts out of the factory module,
Install the HEI replacment,
Hook the wires up from the factory circuit board to the new module,
And you are off to the races.
If you want to go the extra mile,
You can quite easily remove the resistor with your Painless harness,
On on factory harnesses, you can bypass the factory resistor wire with a fresh wire without a resistor.
That will give you full battery voltage to the coil and you are off to the races again with more spark energy at the plugs....
Providing you didn't use a crap coil, wires, cap, ect...
That's why I tell people to do the cap, rotor, plug wire conversion FIRST,
So you can CONTROL more spark energy,
Then worry about the module/coil, ect. that WILL produce more spark energy.
The extra spark energy doesn't do a thing for you if you can't control it and get it to the spark plugs!
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EVLOUTION of the distributor has come a long way...
Original 'Advance' was a lever, usually in the steering wheel, you adjusted as you drove.
The lever had linkage that MANUALLY turned the distributor for more or less advance.
Then someone came along with a spring and weight system to give automatic advance directly tied to the engine RPM,
No more advance lever in the steering wheel...
You know the rules,
If you give someone an adjustment, they WILL jack with it, and usually jack with it until something breaks...
By moving the advance to the distributor, and making it automatically tied to engine RPM,
The loose nut behind the steering wheel couldn't jack in too much advance and damage the engine.
Then someone figured out that VACUUM would compensate for engine LOAD,(and remember, engine design came a long way, early engines produced very little vacuum)
The harder an engine is loaded, the lower the vacuum, and the less advance it will tolerate.
The lighter an engine is loaded, the higher the vacuum, and the more advance it will tolerate.
Your ignition resistor is the same way.
In the early days, BREAKER POINTS ruled the world.
One thing about breaker points, you run a lot of current through them, they will erode and burn away,
And if you run too much current through them, they will weld together.
A resistor knocked back the current through the points, so the points lived much longer.
The resistor is a hold over from breaker points.
And not only did Ford do this, but Chrysler ignitions won't live very long without a resistor in the coil circuit, several other makes also.
The ONLY thing that GM did that was original with the HEI was using a type of switching transistor in it's module that would tolerate full battery voltage.
Every other part of that system is compromised, or is a compromise in some way or another.
SO, we swipe the HEI style module, the most swappable part of that system and use it to our advantage!
People laugh when I say if you swap in the cap, rotor, plug wires from the Ford Version of the electronic ignition,
Use a GM Style HEI module,
And grab an E-core coil from a later TFI ignition Ford,
You pretty much have the cutting edge components, CIRCA 1985!
But sadly, it's true...
The Jeep/Motorcraft is by far the best choice for a distributor,
Solid, Reliable, powerful signal, easily tuneable, parts everywhere,
Upgrade to the tall cap/rotor and some reasonable plug wires to get the spark energy to the plugs,
Get a Ford E-core coil which works best with the HEI style module.
Since the HEI was designed to work with an E-core coil,
And since the Ford version is the best of the factory E-core coils, this only makes sense...
Then get yourself a GM HEI style module,
Dirt Cheap, Reliable, Full 12 volt capable, and easily REMOTELY mountable,
Since coil doesn't care if you have a resistor or not,
And the GM style HEI module will handle full battery voltage/current,
and with the cap/rotor/plug wire upgrade you can CONTROL more spark energy,
You have an 'Off The Shelf' parts ignition that didn't cost you an arm and a leg,
You can get replacement parts in a junk yard if all else fails,
Will pass emissions 'Visual' inspection,
And is about twice as powerful as the factory Motorcraft/DuraSpark ignition,
And generally kicks butt as far as common '12 volt induction' ignitions go...
For those of you that DON'T remember, it was the mid 80's before you could go out on a really cold morning and not have to worry if the vehicle was going to start today or not...
Mostly because of ignition evolution and fuel injection.
WHAT IS THE PROBLEM?!? Thanks 
