"68 tmg cvr on a 73 motor". Neans you have a 69 & up balancer? I can check this afternoon to see if there's that much diff between tmg marks on a 68 & 73.
I'm with Fbody69, need to find tdc on #1 cyl. Then have the rotor coming up just before #1 terminal in cap with tmg mark about 12 degrees before 0 on balancer. Doesnt matter where #1 is on distributor cap as long as you make that your starting point for the rest of the wires.