74 dart swinger, gauge wiring help

I have a 74 dart swinger.....purchased it a few months back...speedo doesnt work, odometer doesnt work, oil/ brake light doesnt work, Fuel gauge doesnt work, only one that barely works is the ampmeter..i pulled cluster out, PIA! Questions i have are.

1. Does speedo need power? odometer or does it just run off cable?
2. the black round plug with all wires labled A-L.....can anyone recommend what each letter represents?
3. on my fuse block what fuse number represents what fuses,wiring?

any help will be appreciated ..i dont mean to sound like an idiot this is just a little out of my relm...i am good at wiring just need some advice on trackin some of this stuff down..

thanks!!:violent1: