vibration at speed

hey lookin for some help. i have a 96 sc2 with 191k and a 5 speed. for about a week i've had a bad viberation in the front end, drivers side, but it only starts at 50, and lasts thru 60mph. worst between 50 -55. the tires are newish, about 7k on them, and i just had them rebalanced and that didn't help. i replaced the top motor mount in june. so where should i look next? it shakes the whole car and engine speed dosent seem to make a differance.