Can you walk me thru this?

[WarpathEngineering]

OK, let's all make the assumption that I don't know what the hell doing.....it's been a looooong time since I've been this deep in an engine compartment and what I learned as a teenager about working on engines is probably best lost anyway!

The Victim: Recently purchased 1978 Chevy K20 350, 4bbl (#17058503), California emissions, HEI, 4spd manual, air conditioning, 140K miles.

It's Condition @ Purchase: Engine started ok but ran with a rough idle, drove rough and the mixture was very rich.

Work Already Completed:
1) Replaced carburetor with rebuilt carb from Guaranteed Carburator (#17058204)

2) Removed smog pump, check valves, manifold injection tubes & associated piping, A/C compressor & associated hoses, EGR & install block plate

3) Replace and vacuum lines to brake booster, heat door accumulator, vacuum advance, 2 fuel canisters (dual tanks), hot air choke & capped all open ports.

4) Replace dead alternator & intermittent starter.

Work Yet To Be Completed:

4) Tune up with new rotor, cap, wires, plugs (Bosch #7973, gap 0.60), pcv, oil & filter change, belts, hoses.

5) Install Sanderson CC17 headers & dual exhaust w/ h pipe.

What's Up In The Air:

I know that with a manual transmission my initial timing should be set at 8 deg TDC and roughly 32-36 deg @ 2500 - 3000 rpm total timing. My question is, with the age of the vehicle and the likelihood that it is still running it's original distributor how do I check to see if my vacuum advance is working properly? Should and how do I adjust my carburetor? Should carburetor adjustment be done before or after setting total timing if at all? Should all this be performed before mounting the headers? Any thing else I'm missing?

Thanks for the help!