Nothing at all wrong with the '78 Aspen brakes, they'll work just fine. They are big bolt pattern though, so you'd need new front rims. And you'll either need a set of large ball joint upper control arms ('73+), or a set of adaptors from Dr. Diff to get the LBJ spindles the Aspen came with to work for you. With LBJ UCA's or the adaptors those brakes will bolt on.
The Kelsey Hayes set up is pretty much the only way to keep the small bolt pattern and still go to disks though.