You don't need to 'convert' anything unless you need to change the flywheel. You can use a starter box on an engine that has a pull start installed.(just to clarify)
WAY more pros than cons.
The only drawback that I see, is that you need a power supply, and you need to bring your truck over to the power supply to start.
It is so nice to start a truck on a box...you can do it with the body on easily...easy to prime by plugging stinger while starting...you can spin an engine longer for those stubborn warm restarts...