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

Hey its your car. If you want limited wheel choises and all the other headaches, go for it. I would opt for aftermarket axles and green bearing in the 8&3/4 with large bolt pattern and 15 inch wheels but thats just me.
If you do buy a 69 K-H brake system, buy it all, upper and lower arms, and swaybar if its there too. Good luck either way