May I make a couple suggestions?
#1 I see mikuni VM32's on ebay quite often. Good upgrade, and often enough don't need a rebuild.
#2 From what I gather, dynas dont last long in cb350's due to certain venting issues. You can use hondamans electronic ignition with the points.
Since they aren't carrying current, they don't really wear out of timing. I'll be using his ignition on my 350 racebike.
Barring finding VM32's, what carbs do you have, exactly?