Dilemma with harmonic damper replacement!
 

Correct part numbers were found.

i know the flywheel on a 350 changed on the 1996 model year because of the one peice rear seal.i bet the 4.3 is also changed for 96.i also think your vortec engine needs it,s origional balancer.maybe you can find used parts from a 96 or up 4.3 marine engine on ebay or in oso,s swap shop.good luck with it.just a thought,the parts you need might also be found on a 96 and up 350.