The factory mounts were hydraulic, so that goop was probably a mix of the old engine oil and the fluid.

I'd check the CV shafts, those will vibrate on acceleration. And double check the torque on the spindle nut, I've had one come loose while driving and scare the crap out of me.

Last would be the control arms, if the bushings are worn they could amplify any vibration that's currently there.