360 swap from van to 74 Duster

I have been looking to upgrade from a slant 6 to a 360 for my 74 Duster. A guy in town says his friend has a 360 in a 70s or 80s Dodge van. He said the transmission is a long tail. What issues will I have making this combination work in my Duster. I realise the driveshaft will probably have to be shortened. Will the wiring harness from my slant 6 work. If the wiring harness needs to be altered, what exactly will need to be done. Will the starter relay, ballast resistor, electronic ignition control unit, etc. all work or will they need to be replaced as well.