Broken Motor Mount on my 1970 440
 

I've got a broken motor mount. The rubber. So, I went online and ordered a pair. Can somebody walk me through what to do and what to expect?
It's on the left side, which appears to be more difficult.
Also, should I do BOTH at the same time even though only one is broke?

I would do both as long as you have to deal with one, but that is just me. You will need a good stout floor jack and the basic tools. If my memory serves me correctly, I don't think you really need to un hook anything except maybe the radiator hoses.
Get the jack inder the pan and jack it up till it just carries some the engine weight. Take the nuts off the long motor mount bolts and use a punch to tap out the bolts that hold the motor mounts to the frame..
Then you can jack up the engine a couple of inches (be careful for clearance all around from the tranny tunnel to the fan.
Once jacked up, I believe there are 2 bolts each holding the mount to the engine. Remove them and the mounts will come off.
Replace the mounts and bolt them up tight, then pick a side and start lowering the jack and get one side lined up and tap the long bolt in, then do the other side.
Once both long bolts are in, then install the nuts and tighten them and that is pretty much it.

That is the way it was on my 440 anyway, I hope this is helpful.