Thanks Ricardo, I'm going to digest this a little at a time. But I want to focus on one statement right here quick:
Originally Posted by RicardoJM
I've run a 78 dizzy (vac retard) with the vacuum ports capped off for a year. There is not anything wrong with running the truck with just mechanical advance; I did notice an improvement once I added ported vacuum (and vacuum advance) - but I got everywhere I was going without it too.
Mechanical advance is just rotating the dizzy to set the nominal advance with the bb on the flywheel right? Right now I have that a little over 7* IIRC. EDIT: the dizzy has built-in mechanical advance based on engine rpm. Vacuum advance gives an additional sensitivity to engine load.
Right now I have the primary vacuum advance can (closer to the dizzy body) hooked up to what is basically the stock emissions hose routing. I think I can play with which advance can I can hook up and which ported vacuum port I hook it to, and as long as I don't have pre-ignition I should be fine. And I think I know what ported vacuum is, but I'm having trouble visualizing which port that is on my carb...