school me on dist

Here a view of all 4 pods, I have read and been told there will be a # on them somewhere. I have looked these over closely with a magnifying glass and I see nothing stamped into any of them except a 6 or 7 digit part # on the mounting arm.

Again Id like to understand better why I need this #, what I will do with this number ect if I am able to find it.

Reading what I can find on-line and will continue to do so.

Id like to pick out the best governor for my own vehicle, dont know where to start?

Thanks for your help on this