1975 duster v-8 front -k-member/ suspension

Does your car have small bolt pattern wheels? Many 75s with slant 6s did. If so, and you change to big bolt pattern disc brakes, you will have to do something with the rear or you'll have two different bolt patterns :(
Another option is to swap the k frame only and leave your drums up front for now. OR (even easier) leave it all and run Schumacher conversion mounts at engine-swaps.com.