msd mag caps?

It all depends on how much you change your timing during a run. You have eight posts on a cap so you have 44 degrees between each post which means that you can move the rotor position up to 22 degrees before it may fire across to the other post. That is providing all your sparkplug wires are in great shape as well as your plugs. remember the high voltage takes the easiest path so if something in the normal path is too difficult the spark will jump. If you are not changing your timing but a few degrees, lets say less than 12* during a run then the big cap doesn't do anything for you. If you move the timing more than that say around 16+ degrees then you should use one.