Wow we have very similar problems. I have a external balance magnum 360 with the same balancer and torque converter as you except I have a weight installed on the balancer. Car shakes a little bit at idle but I'm using a solid motor mount on the drivers side and rubber mounts for the passenger side and trans mount, so I'm basically attributing the shaking at idle to the solid mount which Im fine with. I also noticed one of the ebrake cables was somehow touching between the muffler and body of the car so I need to do something about that.

As far as the pulsing vibrations go mine you could barely feel starting at around 40mph and getting stronger and faster pulses when accelerating around 60mph with them slowing down on deceleration. Had the drive shaft balanced, no help. Noticed the rear wheels were wobbling with the rear end on jackstands so I had the axles checked and bearings replaced (probably the original's from 68) and they were fine.

Then I took a look at my wheels. Turns out my Weld Draglites were actually the Cragar versions and for whatever reason the the center caps didn't quite sit flush with the face of the wheel so thats what was causing the wobble.

I checked the pinion angle on my not so level garage floor and looked like I needed to add 2* shims, which helped a lot! It hasn't quite gotten rid of the vibrations at speed but they seem to have been reduced. I'm waiting to find a shop that'll let me put the car on their drive on lift so I can get better readings.