Round dash plug wires

hello, first post! Lots of good info here! Name is Nick ive recently bought a 76 dart with a 318/ 904. Couple questions. Ive bought a fastlanewest bezel with electric autometer gauges and im getting ready to install but im having trouble finding info on what each wire in the round harness behind the cluster does. Anybody here have that info? Also, my speedo cable is a clip on type and i need a screw on, where can i find a cable that will fit? Read something about pre 67's having the screw on connector? Not sure if thats correct.

Thanks!
-Nick