i think i've found my problem! the guy i bought the motor from (minus flexplate and balancer) said the crank was externally balanced. i looked it up and it said to be internally balanced. it's a summit brand forged 454 crankshaft. the cast cranks are external and the forged unit is internal. that would explain the vibrating. i was asked if i could feel this going down the track the few times it made it. hell i was worried about putting the pedal through the floor. going to try some internal pieces to solve this prob.