I'd suspect the distributor lifting/removal/turning attempt. I'm not sure you needed to do that having already primed the
oil cooler and filter. IMO...that's the one thing that could still may be unsettled. Make sure when you returned the distributor down you FULLY seated the distributor. Sometimes we think it's seated, the bolt is tight as can be BUT if you did not rotate the dist properly (if it needed it) on the way down it seems seated, looks seated, the bolt hold down is seated but the distributor can rise up and down while it rotates. Check the lock down bolt and rotation resistance cold.
Solid motor mounts ? Have them for 6 years. Love the snappier throttle response. I love the instant transfer of power to the wheels. I love feeling every pulse of the motor and love the shakin hands over the wind wings at the red lights ! To each his own ! maybe once per season, usually in the spring do i go over the entire car for re-torqing ...then again we all should do that. The past 2 yrs nothing has moved including the (wire tied) header bolts. Good luck!
Unless your mounts are defective or loose where you should feel the motor shift and clunk, I'd look somewhere else at what you did during your mods.