Can I have your vacuum advance?

What would it do for you? It's in my K-Jet car & it doesn't really do anything extra.

As of right now the only way I can set timing is by using the marks on the crank pulley, not too accurate being that I can't really read it too well. A dwell meter is something that I've been needing to get my hands on to call my own, they do timing as well correct? So I'd be able to sit there with the dwell meter hooked up and set to display timing, and then play with the throttle and distributor to watch where the full advance comes in and at what amount... Is this correct? I guess it's time to go and get one, no more procrastinating.

Timing lights & Dwell meters are normally two seperate things, although you can buy them combined. I wouldn't bother getting a dwell meter, because once you get electronic ignition, dwell will become useless infomation. Just set the points with feeler gauges on the low side.

Do you just set the timing by eye?

And about the carb spacing, wouldn't the 2" air horns effectively add the said 2"? And then on top of that, whatever amount I add on with a little spacer between the carbs and the manifold...?

The twin SU manifold is like a mini tunnel ram manifold, you have runners blending into a plenum chamber chamber & then the carb bolts on top. Adding a 2" spacer is effectively enlarging the plenum chamber. Adding a 2" ram tube doesn't do much at all other than provide an entry with a radius.