Dan,

I had an '84 that had several pounds of lead shot in the rear pylons underneath a plug of urethane foam. You need to take the standard foam plug out of the top of the pylon (it's not glued in, so it just pulls out). Look down the pylon - ordinarily you can see right to the bottom of the pylon. If you can't, and you see the brownish foam - use a long tool to chip away at it until you get to the lead. Be careful not to damage the "shoe" that the pylon rests in that connects it to the sides of the hulls.