[CHEVIBUBBA]

first realize the stock advance curve is a compromise.if you are interested in good fuel mileage/good performance then, go read up on how to optimize your advance.

your camshaft duration has a huge effect on the required advance.
as does the head design.
a stock cam will have a mild factory advance curve that sometimes will continue adding timing all the way up to 4500rpm.not optimum!
a good basic advance curve for a 350 is to set base timing at 10-12 degrees.
have the mechanical advance all in by 300/3500 rpm
for total advance of 36-39 degrees depending on your cyl heads & cam.
i connect vacuum advance to manifold vacuum.this provides for a smoother, quieter idle, higher idle manifold vacuum & brisk takeoffs.not to mention it masks some of the lopiness from some cams.
using an advance curve this aggressive can yield part throttle cruise surging.
for this reason i highly recommend an adjustable vacuum advance.
this will allow you to keep the mechanical advance curve & be able to "pull out" some of the part throttle vacuum advance.
there is some good info on the net. try a google search for:"tuning ignition advance"