Let’s us know the results.👍

Before we get too far down the road, if your engine has a harmonic balancer like this, and a flexplate like this, it could be a heavy rod forged steel crank engine. This era was a real mish-mash with Mopar.

No.

It definitely has the 73 forged crank balancer.

Here is the converter and flex plate I removed.

Here is a photo of the balancer again-

We need to see pics of the front of the convertor. The weights you pictured are to balance a neutral balance convertor, show the front, that's where an external balanced convertor will be balanced at.

Like I mentioned before, I am pretty sure this is forged crank motor that had a miss match transmission set up.
I am an enthusiast not a guru. I am making an educated guess hoping Moparts can massage out my uncertainty.
The vibration only occurred at around 60 mph. 391 rear.

Here are the new flex plate and converter.

Here is the front, no weights. So it could have been just the flex plate causing the vibration?

Okay, that's a neutral balance convertor, no weights on front but the bite flex plate is for using that convertor on a cast crank engine. If your engine is a forged crank engine that is the wrong flex plate for it. Use your new flex plate.

First pic with the shallow drill point cut looks like a cast crank.

.

Thanks for all of the help. I have another question regarding the transmission I removed.
What did this come out of? This section was hitting the frame in the tunnel that the tranny cross member attaches to.
It kept the transmission down a little causing the steering linkage to hit the oil pan when making a right turn. The new transmission tail shaft housing is what I am used to seeing. It does not have that.

If you discover it IS a cast crank engine that convertor and bite flex plate is correct for it and someone has the wrong harmonic balancer on the engine.

That's the snap ring access plate, you need a trans with that plate on the bottom by the trans mount or you could hammer the crossmember for fitment.

:(, ,

I am ready to go.... new transmission in the box,

GOOD, now you just need to find out if the crank's cast or forged before you put that trans in place.

Gods country 340, you have filled in the blanks for me.
Thanks so much for your help!

I should be ready to go when the current event of present time has passed.

👍😎

You said this is in a Dart (A-Body), what oil pan are you using?

A standard big block oil pan doesn't clear the center link/idler arm on a Dart, it has to have a recess in it or be reworked for clearance.

I am pretty sure this is the correct pan.
The second photo shows where it was hitting. I have been sorting this car out for a year and a half. I hop to have all of the gremlins out soon.

While some people say that oil pan is what to use on an A-Body because it has the indentation, it doesn't really work (as you have found out).

Both the 187 and the 699 oil pan have the indentation too far forward (close to the sump area).
They simply don't clear, I've got a factory 69 383 GTS and tried both the 187 and 699 oil pans when I was mocking up everything in the engine compartment for clearance and neither one cleared the center link at the idler arm.
The recess is in the wrong spot to clear.

I ended up using a 7 quart Hemi pan that I recessed my self with a hammer and a larger socket to make clearance.
I looked to see if I had a pic of the recess that I added, but none of the engine pics show that part of the oil pan.

Both the 187 and 699 oil pans are actually listed as C-Body oil pans.
http://www.440source.com/oilpans.htm