Here's a NOS small block one with some "ifs". If the customer wants to spend this much, although this is a good price for a NOS one. I've priced them for awhile. Also, it's listed for up to '78, but I've seen this part number listed for up to '79 and up to '80, so I'm not sure. It would at least give you a lot of what you need to work with. Copy and paste the link below. up

https://www.ebay.com/itm/DODGE-TRUCK-MOPAR-72-78-NEW-MOTOR-HARNESS/232569117226?hash=item3626331a2a:g:8~UAAOSwpCpZstkT&vxp=mtr

Facts are stubborn things.