If you wanted to keep the magnum EFI, its hard to beat the Hot Wire harness. At just over $1,000 it is a stand alone harness that requires 4 wire to be connected for use. There are also wires supplied inside the harness for connecting to gauges and other options. www.hotwireauto,com I've used 3 Hot Wire harnesses, one 5.9 Magnum (into 2 different vehicles now) and two 5.7 Hemi and they work well out of the box. Gene