Can anyone tell me when they started using a externally balanced flywheel on the 350short block. My son just bought a used motor and the older gentleman could not tell him anything about it. We are fairly certain by running the numbers it is a 1987-89 350 but we need more info to get a flywheel.

 

if it is externally balanced it is not a 350 ,all engine's have a harmonic balancer .
if the balancer has a pronounced counter weight on the back side it is probably a 400 small block and a lot larger diameter .
400's and 454's are externally balanced ,better be sure what you have ! 350 will have 4.00 bore 400 4.125 bore with steam hole's between the two center cylinder's on each bank .