ok i have done this its fairly easy. i had a 5.2 magnum from a 92 dakota in my lancer before i decided to do my new build. and i have also done the same with my 1958 dodge pick up. if you use any other automatic other than the a500 ora518 you will have to nitch the bell housing for the crank sensor such as the 904, 999 or 727. or even the a833. this is pretty self explanatory of the position when you mate the trans and engine together.
use the a body motor mounts or those from schuemacker. use a body oil pan with the appropriate magnum pan seals. you can use either the magnum exhaust manifolds. a body manifolds, or a body headers. now wiring is bascally three wires for fuel run and start you can simplify everything by doing away with the relay center from the magnum donor vehicle. just retain the pump relay and the asd.
hook up double dark blue wire of your a body to the blue wire of the asd relay and fuel pump relay. and wire from start terminal from ignition switch to other side of asd relay. to find this wire take a test light and locate at bulkhead connector when you turn key to start. it helps if you have a wiring schematic for both vehicles. here is the schematic i made for my 58 if you can follow each wire from the ignition switch on the diagram you can trace it to its destination on the magnum harness
