Holley 1850-5

What Mike said
but instead of setting the timing to a number, You might try just pulling on the Vcan until the rpm peaks and then retard it enough to lose 100 rpm. This is ballpark for an automatic car with a 2500 or more TC. It will be waaay too high for your 340 stick car at 180psi, so don't drive it too deep into the throttle. But if it likes it, you will now know in which direction to take it.

The reason I say this is too much for your combo is because reading between the lines, I'm guessing your rear gear is 3.23s or less, and coupled with a 2.66 starter gear and guessing 26.5 tall tires, this works out to 9.17mph per 1000 rpm. Idling it down to 600 in gear, which is easily doable, this makes 5.5 mph. With so much timing now ( I'll guess about 20/25*), and 180psi, the power pulses are gonna hammer into the suspension, and the shocks are gonna transfer them into the chassis, and the car is gonna start to buck, and if you let it continue, it will rattle your fillings out.
So this method I posted above is just for diagnostic purposes.
Mike is right about 15* in your combo; but you have to be sure your TDC marks are actually what the engine is seeing. If she liked the Vcan pull, then prove the TDC marks. If you already have, then get another light. If you have a multi-strike ignition, you cannot use a dial-back light on it, unless it is MSD's own lite.
With a hi-compression stick car, IMO the initial should be set quite a bit lower than an auto. The Eddy heads will let you put a pretty fast curve in there. I run mine up to 28* at 2800, from 14*@1000, then I slow it down to 32/34* at 3400. This lets me run 87E10 without detonation. The curve could be a lil faster yet, but at 180psi, there is so much power I ain't chasing after a couple of ponies at 2800. If I am at 2800, it is because I am cruising or granny-shifting, otherwise I am blasting on by.
Happy HotRodding

Oh right, the vacuum advance should be plumbed to the sparkport, and the PCV fully operational,and plumbed to the underside of the primary throttle valves.
15" of vacuum sounds close actually, altho I'm betting that is not at 700 rpm