Where does the timing marks align on a 1987 2.8 s10?

On a 1987 2.8L S10, the timing marks align on the harmonic balancer and the timing cover. You should look for a notch or mark on the harmonic balancer and align it with the appropriate timing degree mark on the timing cover. Typically, for proper ignition timing, you would align the marks at around 0 degrees BTDC, but always refer to the specific service manual for precise settings.