1979 SBC 350, HEI distributor. Bought a project rig and am going through it and found the timing mark on the harmonic balancer is 180 degrees out. For troubleshoot, brought #1 piston to TDC on compression stroke and verified mark is exactly 180 degrees out. Checked distributor and plug wire routing orientation and found correct. Using cyl #4 plug wire to set timing engine runs good. Could the harmonic balance be slipped exactly 180 degrees, or could the harmonic balance have two keyways on it allowing it to be installed 180 out, or could the cam timing be set 180 degrees out causing this anomaly. Baffled. Thanks for your help.