Something to consider: When rebuilding a LOM, if originality is not important, NOS aftermarket Y-Block ‘dual points’ kits may still be available, and a way to maximize performance/reliability.  The included advance plate may even have roller bearings (?).  If economy also is not a concern, advance-limiting devices were offered (Offenhouser?), which allowed a more aggressive ignition curve (lower spring tension).
Of course, a dual advance distributor and a modern carb. would be simpler (and likely easier to set up properly).

6 VOLTS/POS. GRD. NW INDIANA

The Mercury had an additional problem as the Pertronix module would not engage the kickdown of my overdrive circuit.

I have heard that ...

Were you using the IGNITOR  I or II?

Of course, a dual advance distributor and a modern carb. would be simpler (and likely easier to set up properly). 

A DUAL ADVANCE requires a 12V NEG system where the 54 and 55 were 6V POS. This MERC is a cherry and would be a shame to modify. 

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Similar thread from another forum - 

https://www.fordbarn.com/forum/showthread.php?t=349646

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Ok here are the three distributors.

1. FAE 12127-C H342 On the car recently

2. FAE 12127-A2 The one I had spare. No aluminum label, number is raised on the bowl

3. FAE 12127-A H461 The 'NOS' I bought now that came with 13 teeth, frozen pivot and wrong vacuum diaphragm*

*Note I tested it but it held no vacuum, took it apart and found a small 0.10 hole on the diaphragm, I can only guess it was not from a car with a ported, but another one with manifold vacuum

I'll mount the #3 NOS and proceed as follows:

Set initial timing without vacuum attached

Try to test on the car the 5 Teapot Spark Valves I have, and use the one closest to the hg performance from graph hg specs.

Add vacuum and TRY TO adjust timing based on the graph, using the springs I have. Primary spring spring up to 1000 RPM and then up to 2000 with the secondary spring.

One point that I realized too late is that the RPM values shown in my book are for the distributor RPM whereas for the harmonic balance the should be X2😛

Self made, DIY mechanic, too far away...but I love working as much as I like driving🙂‍↕️

KULTULZ and ALANFREEMAN you got it right! I have a 256 ci as confirmed after the engine casted number has now appeared next to the distributor!
Interestingly when the car was imported here, the customs could not find it, they were looking for a stamped number near the water pump as in GM later engines. So my Greek documents in engine they have noted ' without number' 😄

6 VOLTS/POS. GRD. NW INDIANA

Not so.  

Ignition points work just fine with 6V/+grd.,

If the points/cond are for a 6V system

... and the mechanical & vacuum advance mechanisms have nothing to do with electronics.

I do not remember saying that,

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Ok here are the three distributors.

1. FAE 12127-C H342 On the car recently

2. FAE 12127-A2 The one I had spare. No aluminum label, number is raised on the bowl

3. FAE 12127-A H461 The 'NOS' I bought now that came with 13 teeth, frozen pivot and wrong vacuum diaphragm*

OK, it seems the ID PLATE (on some early FYB's and STAMPING NOS on some later LOM are actually SERVICE PN's.

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The only use of dueling points (back in the day) was a longer dwell and a higher degree of coil saturation (especially with a period ignition amplifier).

With today's' TECH, there is little reason (IMO) for them.

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3. FAE 12127-A H461 The 'NOS' I bought now that came with 13 teeth, frozen pivot and wrong vacuum diaphragm*

*Note I tested it but it held no vacuum, took it apart and found a small 0.10 hole on the diaphragm, I can only guess it was not from a car with a ported, but another one with manifold vacuum

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