GM HEI distributors - need info

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I have been dealing with old style points distributors for over 50 years and am good with those, and 15 or 20 years ago I got a used HEI setup, bought the heavier plug wires, and installed all in my hunting Blazer. It has been perfect - no issues.

I have been gathering some used HEI distributors with intent to replace original units in some of my other trucks. Am about to begin the process and need to get rid of some of my HEI ignorance.

Questions:
1. The first 4 GM distributors have the following number stamps:
1103244/6J29
1103337/8H22
1103372/9B14
1112880/4L23
Anyone know if the difference in numbers is significant - or are they all the same item? They all look and measure alike and have the same wiring and innards.

2. Another one looks externally like the above and has the stamp 1103376/9O16, but the shaft is stamped ACCEL 399. On this one there seems to be no inserted "module" and there are only two wires - coming from under the rotor at the shaft - not like the three-wire setups noted above with wires coming from a module. And, the cap ("Standard" brand) has the normal GM type coil bolted on, but there is a contact head - like the top of a spark plug - off to one side of the coil housing. Can anybody tell me what this is all about and how to make it work?

3. I have some new modules to use (hoping that "Wells" brand is good) and am ready to buy heavier plug wires as needed, but am wondering if there is a simple and sensible way to check the effectiveness of the exisiting used modules and plug wires. Maybe for spares? I am no electrical whiz, but do know how to use a meter. Anyone know how to do such checks in a static situation?

4. Any helpful tips and warnings will be appreciated. I have saved two or three posts from this site - explaining the HEI install process - and they seem good. But, as you can tell, I need and welcome good info.

Thanks for any assistance.