Motor Mount Problems?????
 

What are some of the tell-tale signs of failing motor mounts? Any sounds, grinding, etc? I'm pretty sure they're shot, but I just want to make sure.

Mine made a sqeaking noise. Healthy motor mounts look like they are holding the motor almost above them, mine looked like they were losing their grip and looked offset. I replaced mine with a modified convertible motor mount from Western Motorsports in Calgary.

Take a look at your fan inside the shroud.See any feathered edges??
If so,worn motor mounts.

I just got done replacing mine about an hour ago. I had a bad vibration when I revved back 3k rpm and never could figure out what was causing it until a week ago I noticed one of my header primaries was sitting on the motor mount. When I got them out they were destroyed!!!. The car is A LOT smoother now.
Look for header clearance, vibrations, clunking sounds, and also fan clearance.
If you have to replace them, it's not that big of a job, maybe 3 hours max. :D