You've got the positive stop method down pretty good, but I'd suggest marking the flywheel rather than the damper and using the original pointer above the starter as the reference point. Reach through the hole and put a mark on the flywheel at both stopping points. There's enough room behind the oil pan with the dust cover removed to see the positive stop marks clearly, especially if you use something like "White-Out" for marking the positive stop points. Once both of those places are marked, measure between them and divide the measurement in half. That point is the place to put an accurate TDC mark, Maybe a big center punch dot or a chisel mark, and the bellhousing pointer can still be used to set the timing. Since the flywheel is much larger diameter than the damper, it will also be more accurate.
Jerry
Edit: I'd still prefer a delay flash light to set the total timing at cruise RPM rather than trying to do the geometry to get a 36 degree mark on the flywheel or the damper. I've used damper marks on race engines for setting total timing, but it was always done with a degree wheel during an engine buildup.
Jerry
