Airpack for M35

I have the smaller/short air pack and i want to change it for the normal longer one
witch i have right now, but my problem is the electrical component on it.
I dont even know what this thing does? well anyways it is mounted on the side of the short
AP and on the other long one it is mounted right on the end,and the threaded part of it is smaller, and the threaded end of the electrical component on the shorter AP is to big to fit on the other one. What do I do??

Why do you want to change it out?

My other is no good
and the rebuild kit that i had would not work on my short AP
so I rebuilt the other one that i had.

Sounds like one has the hydraulic stop light switch and the other the air op switch. Got pics?

I can get some pics tomorrow