Here is the Rub.
'Pinging' is detonation (and/or 'Pre Ignition' in some rare cases).
Shouldn't be happening at 55.
Check your vacuum advance and initial timing.
(I'll bet you have taller tires and stock gears. This can cause the exact condition you describe)
Jeep used the same distributor from '78 to '90 in everything.
You have the correct distributor.
If you have done the large cap & rotor upgrade you can proceed.
The Ford style E-core coil is a good addition, but won't save lives by it's self.
Here is the diagram for the for the HEI with that distributor.
This is the NO RELAY version, is easiest to wire, but doesn't give a whole lot more spark energy.
You can hide the GM HEI module in your old Ford/AMC DuraSpark module housing, and use the DuraSpark connector plugs to hook this up.
We call it 'Stealth HEI'. Passes emissions testing if you have to deal with emissions testing...
Here is the diagram for using a relay, this will increase your usable spark energy by about 75%.
Relay is common automotive type, used in every vehicle for everything from power seats to headlights.
I get them at discount auto parts stores as a 'kit' for adding extra lights to the front...
When you do this, you have taken all the resistance from the factory wiring harness out of the ignition circuit, so everything is getting as much battery system voltage as it can use.
No factory resistor, no old, dirty contacts and wiring.
Just as much current as your ignition system requires, no questions asked.
You will also need to do this at the alternator.
The diode is Radio Shack p/n 276-1114 and the Heat Shrink Tubing and Small Crimp Connectors came from there also.
With the resistance removed, even the tiny input from the alternator 'Excite' wire will make your vehicle 'Run On' when you shut the key off, this Diode will make that problem go away.
It goes in the 'White Wire', #1 or 'R' terminal wire on the plug to the alternator.
You DO NOT have to do the red wire as shown, just put the diode in, with stripe facing the alternator, in the 'Excite' wire.
You will have to provide the HEI module with two things.
1. An adequate Heat Sink Compound. I use Radio Shack p/n 276-1372A.
DO NOT use the little package of dielectric grease normally packaged with GM HEI modules.
(Grease is clear, Heat sink compound is usually white)
2. The GM HEI module requires a 'Heat Sink' of some flavor.
An old 'Slot One' computer processor heat sink works great,
Excluding that an aluminum sheet roughly twice the size of the processor will work.
Must be flat, clean and a good heat conductor.
Here is an example I did in copper.
The next thing we need to discuss,
Is ONLY IF you don't keep the new module in the location of the old module...
The Orange & Violet wires from the distributor are very sensitive!
They MUST BE KEPT AWAY FROM SPARK PLUG OR COIL WIRES!
Keep the pair twisted around each other. This helps keep out EM & RFI.
Keep the pair on or attached to the block when running them to the fire wall, then run them along metal to their new home. Metal is your friend when it comes to blocking RF & EMI signal.
DO NOT run your mag trigger pair in the same harness with the module & coil power wires! Just this much switching noise will affect them.
If you use the pair in the harness to trigger you HEI module, they are all ready twisted, protected and segregated.
This is the best you can do with a 12 volt inductive ignition. The next step is a MSD 6 series fully CDI module.
Anymore questions or problems, I'll be checking this board pretty regularly for the next few days, so don't hesitate to ask.
Semper Fi. Carry On.