it you motor is shaking i think you have problems. motors now adays are built better then back in the 60-70's. they come somewhat balanced from the factory. have you ever seen the wineglasss on a valvecover demo?
I was just at a site with instructions about filling mounts with Windowweld a couple of days ago. I forgot the address, but they basically just said to fill the voids with the Windowweld and let them set for a few days. Doing one at a time might be a good idea.