I can really see the benefit of urethane bushings in the suspension, but I'm not entirely sold about their added benefit for the body mounts. Their rigidity is awesome for steering response when used at the control arms and sway bar points, and I can say that because I did the Chevelle with Energy Suspension graphite impregnated urethanes about 10 years ago (wow! time flies) and my wife's Honda Civic just recently (oh man her bushings were GONE!!!!) But it may be too much when used everywhere. I've heard (yes, "I've heard", this is not from first hand experience) that urethane body mounts make for a significantly harsher sounding ride. I like the conceptual idea of rubber body bushings absorbing vibration and road noise (more so than urethane) and when it comes time I will probably do the Chevelle's or Camino's body mounts with rubber. It's not a matter of longevity, as the originals are over 42 years old now and still very serviceable. And I do believe that rubber bushings sets are cheaper (don't know for fact.)
As with everything, your mileage may vary. Just another opinion to consider.
And +1 on Keyser's anti-sieze comment. It's a regular habit of mine that if I remove a bolt, to put it back with anti-sieze (in most instances.)
Good luck.