There will be many opinions on how to set timing... Usually a good rule of thumb is 36* total mechanical timing all in around 2500 rpm. With an initial (idle) timing somewhere around 8-12-16*. This depends on many variables including static and dynamic CR of the motor, fuel octane, altitude, and on and on....

What kind of ignition system do you use? Vacuum advance? Timing should be set with vac advance disconnected and plugged...

I would start at 36* degrees total (without vac) drive it a bit including some wide open throttle then check the spark plugs. You can read the plugs to tell you whether you need more or less timing based on the heat line on the ground electrode of the plug... you want this line to be at or just past the bend in the electrode... adding more timing moves this line further from the tip...see this page for more tips on reading spark plugs (I'm sure there are more/better resources but this one is pretty good):
http://www.dragstuff.com/techarticle...ark-plugs.html

There are links to other related articles on that same page...

As for your off idle stumble that is usually accelerator pump shot too small or too late... usually bigger pump nozzles cure this problem... could also be an indication of vacuum leak or excessively lean mixture...

There will be other suggestions from more experienced folks here but I hope this helps in the meantime...

-Chris