I currently have an old vertex on my motor, but I want to switch to a newer mag. I've been looking through some catalouges and I see that Mallory and MSD both make mags, can anyone tell me the difference between these two mags besides the price. My buddy runs a super mag and he has to run two batterys so he can spin the motor fast enough to produce a spark when he starts it, does the same go for a sprint mag. Also we are currently running a 671, but we are planning on switching to a 12 or 14 in the near future, should I buy an offset mag now, or can I convert it later. Lastly what do you think my old vertex is worth? Any suggestions are greatly appreciated