Check the engine numbers on the rear of the block, drivers side of block. Go to Mortec .com and check the numbers, in the 80's the rear seal was changed to a i piece seal and the flywheels are different. As 78 buckshot said the 400 has external balanced flywheel and harmonic balancer, you don't want to put that on your engine. If you do it will shake so bad when running you will loose every dental filling in your mouth.
