A quote from the Professional Products damper instructions:
We have made a running change in our 6-3/4" SB Chevy 350 dampers #80000 and #90000 by adding another TDC mark which is labeled "Vertical TDC." This is for those engines produced from 1984 to 1995 which have the TDC mark at
the top of the balancer and are timed by looking down behind the water pump
to view the timing pointer. Use an aftermarket timing tape if desired."
Use the '0' zero on your balancer.
Here is what I do for adjusting lash and preload, This method works best with degreed balancers with marks every 90 deg.
Start with zero, #1 on TDC. Adjust #1 Intake and Exhaust, rotate engine clockwise with turning socket by hand 90 deg. and adjust #8 Intake and Exhaust...then another 90 deg. and so on.. 1,8,4,3,6,5,7,2. and you are done. Basically you are following all the TDC events in the firing order. Two full turns of the engine is all you need.
That's the method to my madness anyway.