Wiring for electric choke
 

I'm hooking up the electric choke kit in my boat. I have most of the wiring harness untapped. I would like to know what wire I could tap into for the + side of the choke? I thought I could use the purple, but the directions said not to use the wire off the coil. The + side of the coil is purple, so I'm not sure if I should use this? Can I use a stud off of my alternator? If so, which one? Any help would be appreciated. I have a 454 97, I'm not 100% sure what year the wiring harness is from, but it seems like it pretty much matches up to a 96 gen V carb 454 mag. In one diagram I have, is shows the + lead being pulled off the alternator, but I'm not sure which terminal I should pull it from? The alternator in the pic has 4 studs. Mine only has 2 studs. Maybe the one in the pic has metal straps connecting some of the studs? Thanks for any help.