'83 245 Diesel

I've been getting an entire car shaking vibration when I brake but also when I down shift. It seems like the worst of it is coming from the rear end, which leads me to think that it might be the bushings back there?

Brakes looked alright, and I didn't see any excessive movement in the bushings upon inspection. They do look pretty cracked up, so I'm wondering if enough play on the axle could cause it to jump around, which is what it feels like.

Also, there are rub marks on the inside of one of the wheel wells. I'm assuming that the axle must have moved over somehow to make them. I also just drove across the country with a pretty heavy load, so might that be a factor as well?

Any advice is appreciated, as this thing feels rather unsafe to drive as it is and I've still got more driving to do.

Thanks,
jt