shuttering vibrations

my 93 labaron gtc has a shuttering vibration at 38 mph. once you past this point or before this point everything is fine. I read that this problem is either due to an incorrect firing secquence or the torque converter. Any information would be helpful:screwy:

Could also be that you are in need of a front drive axle or two. I'm pretty sure an incorrect firing sequence would be felt as well as heard at any speed including idle.

Also may want to check your wheel balance and tire wear.