The "ready-to-run" feature these companies are trying to sell, isn't really ready to run at all. All that means is there's no control box.
They all will still need advance curve adjustment for your particular motor and application.
I prefer using the Duraspark ignition for the sake of parts replacement.
I get my distributors from Parkland Performance in Tacoma WA. They take your engine specs, cam card, vehicle weight, gearing, tranny type, and vehicle use. You get a complete rebuilt Duraspark distributor that has the vacuum and mechanical advance set up for your engine and application. They also include a recommended initial timing setting.
All for only $200.
http://reincarnation-automotive.com/