Sorry if I'm based on my English knowledge missing something, I have stock engine 5.9L that was injection and now it's carb. no other modifications, in terms of "CURVE" what I'm missing? what does it means? is there any exact model I need to buy?
I agree with Halifaxhops. It will be easiest if you buy a distributor that has the curves close to what the engine will want.
If the car is 1973 or later and still has original wiring, a distributor for a 1990s Dodge truck using a Chrysler type amplifier will be easiest.