When I go over speed bumps I feel a good clunk in the floor. I have the upgraded front driveshaft and the rear has no play. The disco is new to me and not sure if there's a common place to check? Also a decent vibration around 60-70??

 

Look at the Motor mounts (2) and Trans Mounts (2). Then inspect the rear bushings for play.

 

Is you 1" lift, spacers if so you are still running on a very warn set of factory shocks.
What have you checked so far??

 

My old Disco clunked at the back and it turned out to be the Watts linkage bushings . Wasn't complicated to fix, just a PITA.

 

My disco would clunk when the suspension was compressed going over speed bumps...turned out to be a bad shock.

 

Do you feel this clunk in the floor when going around tight turns or only on sharp bumps? Mine was making a slight vibration at highway speeds recently and it was the rotoflex that had a slight tear in it. Replaced that and vibration was gone