Charging Issue (72 Blazer)

[snuff]

Just purchased a 72 K5 Blazer, and it turns out there is a charging issue. While the motor is running, I only read 12.5 volts on the system (freshly charged battery) opposed to a normal 14.2 volts. I have replaced the Alt, Reg, and it has a new battery. I am told that on the alt, the F term should read 12 volts when the ignition is on. Well, I'm not getting it. On the reg, I am only getting a 12 volt reading on the number 3 terminal which I understand is the cable running from the Alt to the battery. My guess is possibly the wire running from the ignition to the regulator? What are your thoughts. I appreciate any help. Thanks in advance.