3.09 gear set with 3.23's

MOPAROFFICIAL said

Tail shaft bushing, have you ever replaced it?
Is there a dent of any kind/size on the driveline?

The drums, have they weights or balance marks on them?

Is the vibration centralized to the firewall trans tunnel and do you feel the steering wheel vibrate when it occurs?

Is it in the rear of the car and does it pulsate?

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I’ve replaced the tail shaft bushing, trans mount.

swapped in a 904 (bought specific b&m plate)

ran a 4 speed for awhile

different driveshafts on all of the above.

pulsating vibration from rear/seat
Changes with deceleration.

I believe it did it without axles/drums but it’s been awhile.