2 things. #1, if you still have the ballast restistor hooked up to that truck, then you likely only have 6 volts to the coil WHEN RUNNING. Do not check it with key on. Of course you will have 12 volts then. Points igniton back in the day, would get 12volt to the dizzy while motor off and while cranking in the start position, then once started an in the ON position, it drops to 6 volt using a resistor wire off the ignition or wire through a ballast restistor. So if you have the ballast, its likley 6 volts and HEI electronic ignition requires 12 volts full time.
#2, yes, vac advanced should be hooked to ported vacuum on the carb, not full time manifold vacuum. If you need to figure out which vac port is which on the carb, use the carb # and search the internet for the carb and identification for installation. If you are going to hook it to manifold vacuum, then you may as well just adjust the time to full advance, and leave the vac disconnected. The only other way, and you shouldn't need to worry about it at all on that truck, or any truck in OK for that matter since we do not have smog checks here, but, you would also see ported vacuum go to a water temp switch aka TVV or TVS (Temperature Vacuum Valve or Switch) in the manifold, then out of the switch to the dizzy vac advance ball. The reason this was done, is so that the vacuum could not advance the timing til the motor reached a predetermined temp, like 140-160 degrees, this gave a reduction in NOx (Nitrogen Oxides or Oxides of Nitrogen) which is know as air pollution, til the motor was warmed up and operated much more efficently. You also may have a dual ported TVV or TVS where the EGR Valve is also connected the same way so that the EGR remains closed until the motor warms up to operating temp. I don't even know if you are running those devices, most people don't thinking its "Just a Smog Device" not realizing it has a benefit to your motor too. EGR, (Exhaust Gas Recirculaiton) Brings or allows a small portion of the exhaust gases into the intake system diluting the air/fuel mixture which will reduce NOx, but also reduced the engines need for octane and reducing possibility of pinging. But, you'll never hear that. What you will hear is take the EGR off. So actually an EGR vavle can be beneficial to your engine, but theoretically, yes its detuning the engine, but at the same time, its also allowing for more timing advance and avoiding a ping on lower octane fuel all while reducing NOx at the same time. Didn't mean to get down that rat hole of explanation but now you know. Most people don't like smog devices becasue they say they rob power. They don't rob near the powe most people think. The only reason I don't like smog devices is because they are usually in the way when trying to work on somthing else to the motor. I've been know to hook up more smog devices than disconnect. If I buy a used vechile and see all those sitll in place but vac lines are capped off, I'll follow the vac routing diagram and hook all that junk back up and really don't see a noticable loss of power, but do see an increase in fuel economy. Just saying, if you have the TVV use it for your vac advance, if you have EGR hook it up too. Just make sure the pintle in the EGR valve is not stuck. If it is, take it off, clean it, and reinstall. Then you can run 87 octane and probably get a 1/2 to 1 more mpg, maybe even more if you have other vac leaks and found them while hooking up lines to the TVV, EGR and Vac Advance on the dizzy.
