I did something similar with a 1972 Powerwagon crewcab. Bought a low mile 5.9 Magnum which was OBD 2. Removed a complete wiring harness from an early Dodge 1500 with OBD 1. Less sensors. From headlights to taillights including column and dash, fuel tank etc. Installed it all, primed the fuel system and it fired up the first time I hit the key. The worst part was removing the wiring harness from the Dodge. IF I wanted to do what your thinking about that is the route I would go. Buy a whole car and start moving things. All the aftermarket stuff is great but it's not the only way.