Coupe lurch

[tbrown@nosc.mil]

     My 86 Coupe GT, 5sp and 130K miles has slowly developed what I can 
     only describe as a drivetrain lurch.  It is present when I let up on 
     the accellerator while cruising in 5th gear.  It is most noticeable 
     when downshifting into 4th gear accompanied with immediate 
     accelleration (e.g. when overtaking).  I then get an alarming clonk!
     
     Do I need new motormounts?  Do they get squishey after 10 years or so? 
     I replaced the transmission mount last year which helped a bit.