I am sorry that I wrote about distributor parts as in general.
Since I use MSD 6AL(similar system) in my car, I automatically have 20 degree crankshaft rotation spark duration which covers pretty wide range of timing.
Please see below URL.
http://www.msdignition.com/1ignstre.htm

I hope you also go for MSD to see how much improvement your car can have.

Ezzy.