I need some help with an old Dodge truck.

You can wire it either with or without a ballast,

1....without you must use a coil designed for direct off a 12V system. Many tractors do this. Depending on the key setup you may not need a bypass circuit

2...I tend to WANT to use a ballast. As I said, a ballast helps stabilize coil power and helps keep points from buringing and damaged coils. The bypass circuit also gives you a nice hot start when starting----Remember---when starting, and especially with a 6V starter on a 12V system, the starter pulls down batt voltage. With a 12V coil, it gets low voltage when starting

If you stay with a ballasted system, then when cranking, and with the bypass circuit, you STILL get hot voltage to the coil for starting