back to the early posts, why wouldn't you be able to use the explorer serpentine set up on a 28 oz damper for the 351 as was eluded to in post 9 & 12?
I am using the explorer balancer (50oz) for the 351w. The rotating assembly actually balanced kinda funny and I think the (scat) crank is to blame - they used the 50oz balancer on the front, but needed a 28oz flexplate on the back. They had to weld (add) a little material to the flexplate, but not very much. There was very little material removed from the crank this way. If not for using the 50oz in the front, I think they would have had to add mallory metal to the crank, which gets expensive really quick.
Eric