I am planning to replace the body mounts on my 78 this winter.   I have a few questions that some of you might be able to answer for me. 

I have used a 2x8 and jacked on the floor sections to replace one body mount at a time. I use the polyurethane bushings with a little white grease on each side before install helps stop any squeaks. There was a post listing the things to do for body removal this will give you a guide line,  a little more than you will need but a good check list

  I did it the same way. The Body dosn't weigh all that much and so its not that hard to Jack up if Your only going a Couple of Inch's. Disconect the Brake Lines at the Master Cylinder and the steering at the Rag Joint. Parking Brake Cable should be Ok as long as its released. At this same time You Should think about replaceing the Fuel Lines cause Your going to have to do it all over again if one goes bad. Keep Real Close Track of the Shim's that are between the Body and Frame and make sure they go back in. If Your Car has much Rust You may want to replace them at the same time. If so You will need to Lift the Body some 3-4 inches to Access some of them. As long as all the Bolts are Loose You should be able to do one side at a time.