Truck won't start doesn't have 12V

[pound41]

Hello I have a 1971 chevy blazer. I had to redo the fuel system then mess with carb and a fuel pump putting out too many psi. So I have been cranking and starting it a lot lately and it has been fine.
The truck has a Mallory Unilite distributor that I didn't install, I have the same unit in 3 other trucks so I am familiar with the unit. I was looking at how to test the module According to Mallory with the key on I should have 12 volts on the negative side coil. The coil is brand new. I have 6 volts on the negative post.
Any ideas on where to start. Thanks