So I took my car ('72 Duster) to a local car show a few days ago. The car started up and RAN FINE with no issues at all, on the way to the show. After show was over,
I started the car up, let it idle till it got to about 140-150 degrees, as I always do. When I left the showfield and got to the main road, I shifted gears, (it has a forward pattern manual valve body)...and once I started to shift into 2nd gear at 35-37 mph..all of a sudden car made a loud "POP"!!! noise, and it completely died, lost power steering, and had to quickly pull into a nearby parking lot. The noise from the car sounded alot like a loud fire-cracker going off!

Now... there is no electrical power at all,...no interior lights/headlights, although the electric fuel pump still runs when I turn it on. And I checked battery, (Optima Red Top gel style) it holds a charge. Engine is a 340 block stroked to 418 ci, with a solid mechanical cam, and adjustable 1.5 Indy roller rockers, an 850 cfm Demon chokeless carb, single plane Edelbrock Victor 340 intake. I am at a loss here...any help would be appreciated!

how is the fuel pump wired in?

fuseable link?

if your battery is good, I would be looking at the fuseable link or bulkhead first.

see if you have battery voltage at the back of the alt as well.

It has a fuseible link for fuel pump. What would make the loud POP! noise all of a sudden?? And then the car just shuts down? Bad wire somewhere?

I think that might be coincidence.
you blew the fuseable link to the main harness, shuts down all electrical including spark.
excess fuel into the hot exhaust and pop like a shot.

if I were going to bet, you probably started over charging due to a bad VR, blew the fuseable link and it died.

but that is just a guess without doing tests with a voltmeter.

it sounds like it popped & died at the same time. will it crank over jumping the starter relay?

Depending on where the POP came from (tailpipes?), take a look inside the distributor cap and at the mufflers:
The cap to make sure the rotor & center electrode are fine & no carbon tracking.
The mufflers to see if they look a bit swollen, or worse, from fuel lighting off inside.

Had a similar deal, though it didn't interrupt electrical power, on a vehicle a couple months ago.
The center electrode in the cap had apparently dislodged & been hit by the rotor's tang, leading to a crossfire.
It had been running perfectly until it started backfiring a few times.
Oddly enough, it stopped backfiring and I drove it home (about 5 miles), during which time it ran fine, as though nothing had happened.
Poking around, one muffler was swollen, the other side burst, and the cap & rotor looked like they'd been in a fireworks show.

It did make the POP sound, and died at the same time. I have not tried to jump starter relay. The mufflers look okay from the outside anyway (it has 3 inch exhaust to the bumper). I will have to check the dist. cap when I get time. Do you think the pushrods, or valves would get damaged in any way from this? How about power valve in the Demon carb? The answer Andrew gave about the fuselink blowing, and overcharging, seems a good possibility.

So, the "pop": was it a backfire from the tailpipes, or from the carb, or somewhere else?
If it was from the carb, I'd certainly check the PV, but I wouldn't expect it from an exhaust backfire.
I can't imagine a backfire either from carb or exhaust to CAUSE valvetrain damage.
In the old days, you could tell an exhaust valve was bad by a sustained light popping through the exhaust; engine would run, electrical would be unaffected.
Popping/backfiring could be a symptom of a valvetrain problem as opposed to a cause, doesn't seem like that's your problem.
Never had a scenario where an engine malfunction would kill the electrical system; I'm guessing something electrical is the root problem.
You're gonna need to check a few things out, and report back.

I don't know where the sound/noise came from? I wasn't expecting it, and it happened so fast. It didn't feel like a backfire...like I said before, it was one loud POP..like a firecracker being lit! And then the car lost all engine/electrical power. From memory, I would lean towards the sound coming from exhaust though.
I will have to check some things over as mentioned, when I have time, and report back.

If your battery is relocated to the trunk, read Stanton's comments on this thread: https://board.moparts.org/ubbthread...nd-for-battery-in-trunk-this-tab-ok.html

Nope, battery is in the stock location, at front left inner fender corner. When all this happened, there was no burning smell from anywhere, or any "smoke" for that matter.
I have yet to start checking things out, since I have been busy with other things, family wise.

After finally getting a little time to check out my car....upon closer inspection, of the bulkhead today, the fuseable link wire is literally burned in two! So That I assume caused the total shutdown of the car, when I was driving it. Now I need to figure out why the wires burned up. I will take Andrew's feedback, and check out the VR, and probably the alternator as well.