Be aware that some disc brake setups push the wheels out further(up to 5/8"). That may mean the wheels you have or want to have may not have enough back spacing and you will have tires that rub the fenders. Good news is there are some disc brake companies that make zero offset components. Be sure to check that the system will work with 15" wheels since there are some that don't.
For 15” wheels, CPP offers a zero offset kit that doesn’t push the wheels out. I’m actually looking at gen 4 F body disc brake applications. They are a very minimal offset probably less then a 0.25”. Basically, the thickness of the rotor hat. There are a lot of people converting to the 98-02 LS brakes. They are 12” rotors and will require going to larger diameter wheels 16-17”. The 93-97 F body brakes are a similar setup but will allow the use of 15” wheels. This is what I’m looking into. While I like the latter 98-02 setup and going to a larger diameter wheel does not bother me, I would like to be able to run 15” wheels if I choose.