I'll repeat myself...until you get that timing up to around 38*, you're wasting your time, and everyone elses. The timing is going to affect your idle quality, vacuum, all carb adjustments etc. So everything that you're doing, you're going to have to re-do once you get the timing where it needs to be. Iron headed FE's need 38*-40* and will run best that way unless you've got other bigger issues such as bad combustion chamber deposits, a bad vacuum leak or a big squish area in the combustion chamber making it prone to detonation.
Aluminum heads need less timing, generally about where you're at now. The stock iron heads need more. If you don't believe me, check the factory specs.