Pulsating vibration while cruising??

Update: Pulled the diff, changed the pinion bearings and put it back, still vibration.

some answers to ur questions: I have schumacher motor mounts, plugs looks pretty good. As the axle bearings where changed before i bought it (1 year ago) and can't hear anything i reckon this is good.
U joint is good in the pockets.

I know that my converter is missing the external balance weight, but didn't think it would matter this much. Anyone know where i can get these weights and where to mount them on the converter?
Also thinking front tires are bad and unbalanced as they are stock with the car so will be changing these also.