The master cylinder may have the same job, as you say, pushing fluid. But not the same amount. Disk brakes generally need more volume moved, especially with multi piston systems, meaning that your drum brake master will run out of travel before completely pressurizing the front brakes.
I'm guessing here but the the booster is looking for a disc brakes in front, ie: it's going to provide a lot of boost to move those disc brakes but you have drums in front that don't require that much boost. Because the discs use up fluid as the pads wear down and have greater travel on the pedal than the drums require, the booster may give you a real touchy pedal. Were I you, I'd get the booster and consider a retrofit of front discs, new proportion valve and new front brake lines. But if you try to install it to see how it works, be prepared to deal with some fitment issues with the pedal push rod fitting to the booster and the booster push rod fitment to the original master cylinder. I wish I knew more about Mopar brakes, but I can tell you when I had my '69 Roadrunner I always ran drums with good shoes and power braked to heat the tires up and never had any problems on the street with fade or having to stand on them to stop. Good luck!