Ok so I am getting ready to install a 351W HO from a 1984 F-150 and want to make sure I install the right Harmonic Balancer, I am going to use the flywheel from a 1973 302 3 on the tree, will this work with the stock balancer for the 351W, it had an automatic C-6 tranny in its previous life

 

Yes because all 351W's had the same imbalance as the early 302's did. Only 302's went to the higher weight in the 80's.