As far as springs go. What rpm do you idle at? You need to run springs stiff enough to not allow any centrifical advance at idle. Some engines can idle at 700, some need to idle at 1000. The engine that idles at 700 can run lighter springs than the engine that idles at 1000. For the engine that idles at 1000 or above, you have to keep adding a stiffer spring until there is no centrifical advance at idle. (the point is you do not want to use up any advance at idle, and then let it advance as soon as it gets off idle).
When I recurved my 68 340S with a 484/284 cam and idle at 900 with stock mopar electronic ignition. I ended up using the stock light spring and one of the lighter springs from the MP recurve kit and blocked off the vacuum advance. Set the timing to 34° total which then backed down to 17° at idle.
