[mr0077]

H dog, man, I got no idea what to suggest...except check it again (lotsa work)! You described exactly what I did to mine, except my indicated TDC was almost exactly spot on with the measured TDC. What you're describing sounds like the pointer is in the "rong" place. Is there more than one timing cover for your motor (Chevys have at least two)?
If the timing pointer is in the wrong place, you could either mark a new TDC (and 10-degree BTDC mark) on the damper, and use the timing mark you have, or reverse the procedure using the piston stop, except mark where the damper TDC stops on the timing cover, split the difference and move the pointer to that location.