I found a 1980 chevy that originally came with a 350 v-8 and a th350 trannie. Now it has a 454 from a '76 with the same 350. It has a terrible shaking problem! IT does not smoke or knock! The motor mounts and trannie mounts are new. The complete bottom end has been gone through and it still shakes. Crank,bearings,timing gears and chains! The trannie has also been rebuilt! I am starting too thing the previous owner did not switch the flywheels. what do ya'll think? Motor is tight but just shakes a lot!!!