can someone please help my car started vibrating really bad at about 1500-2000r,s really bad a couple weeks ago its a 87 firebird formula wit a 78 350 4 bolt transplanted in it after i destroyed the lg4with a 700r4 tranny in it at the above rpm my car vibrates really bad in every gear i balanced driveshaft ,tires,new rearend,motor mounts front end steering components and its still there and if i hit neutral and rev it up it wants to lurch forwardcan someone pleasew help im out of ideas:hail: