Back Up Lights Dont Work

I have a 1973 Duster 340 A833 4spd I cant seem to get the back up lights to work I baught a new switch new harness still nothing the main dash harness is out of a 74 valiant the engine harness is new reproduction,There are two connectors grey at the back of the engine one comes from the wire block on the firewall the other dont really know yet havnt untaped the harness not sure if I got them right but tried switching still dont work any help would be appeciated
Thanks in advance
dgtwo