TIMING?AGAIN
You can use a threaded positive stop in the spark plug hole to find true TDC. BUT BEFORE YOU USE IT, take the rockers off that cylinder or you can bend the valves.
If your balancer is marked in degrees before TDC, screw the positive stop in to stop at 30 degrees. Then measure carefully the distance from zero to 30 degrees and put a mark on the other side of zero at that measurement. Rotate the engine backward slowly till it is against the the positive stop again. If it stops at 30 degrees, your timing pointer is correct. If not, move the pointer until it is equal degrees on both sides of the positive stop.
If you only have a zero mark on your pointer, just pick any measurement around 1 inch and put that on both sides of your zero mark and move your pointer until the measurement is equal on both sides of mark.
Morroso, Manley, MR Gasket, Comp Cams and others make an aluminum threaded positive stop.