78 Magnum and 78 Power Wagon in Local Pickapart

It loiks like that magnum has the gage cluster with tachometer thats a hard to find gage panel. You need to unbolt and get the entire cluster assembly, with printed circuit card on the back and get the auxilliary wiring harness for the tachometer. This whole setup is unique to the tachometer equipped 75 up chargers, magnums, cordobas. May be worth some coin to the right person if you get it complete.

Btw, the magnum has a 4bbl carb, unless somebody added that to the engine, more than likely its a 360 . The 318s for that year were 2bbl only.