If I am replacing my ignition coil as well as cap and rotor as MSD, do I need am ignition box?
Huh?? What engine is this on and what are you doing to it?
Replacing the distributor cap and rotor to an MSD brand and replacing a stock coil with an MSD coil. Nope, neither require an MSD electronic ignition unless you are changing the points or pickup to an MSD pickup.
Maryland School for the Deaf?
Merck Sharp and Dohme?
Motor Sports Developments?
Marine Sanitation Device?
Moscow Summer Time?
Mass Service Disruption?
Multiple Spark Discharge
Unless you do all out racing and live in the very high RPMs territory you don’t even need any MSD components.
MSD is a brand name for aftermarket ignition systems and parts.
If you are swapping from conventional ignition to MSD, sometimes there’s an issue w/the ballast resistor in the coil primary circuit. The instructions should explain what you need to do.