Will front disc brakes off a 69 dart fit a 74 scamp???

an easier way for him to identify the brakes is to ask , single piston floating caliper or 4 piston fixed caliper ?.

Now Can those disc brakes be put under your car ? Yes.
Would it be wise to do so ? No.
buy the K-H brake system if the price is right, then offer them as trade for 74 correct setup.