As a permanent solution, it would probably be better to build a stand alone harness/fuse block for powering up the PCM-that way you are not relying on any potential issues with the existing '67 harness. Here is a link to the page on the lt1 site. Near the bottom of the page it shows the fuse block that gets key hot/battery hot power to run the PCM independently of anything else.
http://lt1swap.com/2000harness.htm
As a temporary measure, you can locate the pcm, fuel pump, and coil wires and connect them to a key hot or battery hot circuit. Then tap a direct, heavy wire from the battery to the starter to kick it over. You may also want to temporarily bypass the pcm controller for the fuel pump, and just feed a key hot line to the fuel pump. The pcm will only allow the fuel pump to run for a couple seconds without sensing the engine cranking over. Even if the engine is cranking, you are not certain that the PCM is sensing it if all sensors are not hooked up properly. I try to remove as many variables as possible until you can pinpoint the problem.