Welcome to the 'bolt. Help us help you by telling us a little more and answering some questions.
A '57 Chevy did not have disk brakes, so no that doesn't sound right.
Or do you mean replace the front axle with a later one, and use a disk kit for the later axle? That might work to a degree, but a 1-1/2-ton truck needs bigger brakes than the common disk kits.
If you want to maintain the current load rating your project is a bit more challenging. What are you trying to accomplish, and what wheels and tires do you plan to run?
How do you want to use the truck and why are you converting to disk brakes?
I'm not trying to challenge your decision, but rather better understand what you want to accomplish.
