Editing Upgrade factory novs disc brakes

Hello, I just purchsed a 1970 Nova that has been dismanteled by the original owner. The car has factory disc brakes in the front and I would like to upgrade them to a larger rotor. Searching the internet I see alot of conversion kits to go from drum to disc but I really havnet found an upgrade kit for existing disc brakes. Does anyone know where I could find this type of kit and if there are multiple suppliers, which brand do you reccomend?

Thanks,