This question has been asked, and no-one had the correct answer. There is NO MSD product for the 3.3L V6 SC or NA. From MSD direct:

Dear Sir,

Unfortunately we do not offer an ignition system for your application, the factory ignition on your application has a transistorized/coil assembly, and with this type of set up you will not be able to adapt an aftermarket ignition. If you do try to install it, it will damage the transistors internally and will not start on factory ignition, plus the transistor have to remain in place for the factory ignition. We are in the process of coming up with an ignition system for your application, but there is no set finish or completion date.

Thanks,
MSD Tech

From what I have heard, an aftermarket ignition wouldn't do you any good unless you had forced induction, or some heavy engine mods.

Is this true?

With a higher voltage, you can increase the spark plug gap, which will give you a longer spark, which will in turn burn the fuel faster (eh maybe.. who knows).. this should increase power & economy..
Thats the theory anyway.. bigger spark is all you are going to get with aftermarket..
the other thing some of them do is multiple sparks, all in a very short timeframe, or 1 really long spark.. I don't know about those tho..
I would figure if the fuel/air lights off with the first spark, what is the next few going to do that the already burning fuel charge won't? You light a blowtorch, and it's lit.. why continue playing with the sparker once it is already burning?

Atleast that is what the selling point is. I would like to hear from a mechanic on this...

Traditionally MSD ignitions will provide multiple sparks across the cylinder burn. It helps to ignite unburnt fuel. I see your point about lighting the blowtorch, but internal combustion is different it is under a lot of pressure. Every engine out there lets some unburnt fuel sneak past and even get out the exhaust. During emmissions testing they even read how much unburnt fuel is escaping. The MSD will also provide an eratic combustion, which will scatter the burn across the cylinder providing a more powerful piston thrust, which in turn provides more power and better economy.

I had a Jacobs system on my 88 Pathfinder and it made quite a big difference in performance. I ran it for about a year before I traded to another vehicle and had no problems in about 30,000 miles of driving.

Yes, there is unburnt fuel, the fuel only burns if it is in contact with oxygen.. there are pockets of to much fuel, and not enough fuel..
If the "explosion" on burning fuel in the cylinder won't burn these pockets, why would a spark, with far less energy do it?

I was told that I could use a MSD 6A ignition with a blaster coil on my X.......am i wrong?