Yes you can use the disc brakes from the Volare/Aspen cars on your A body Scamp. Do not bother with the F body (aspen/volare) upper or lower control arms, they are very different and do not fit.
Spindles, dust shields, calipers, rotors, caliper mounting brackets, hardware. Get the master cylinder and proportion valve/distribution block with the connecting lines between them as well if available. I'd also take the brake hoses for comparison on the new ones you'll have to get.
You can get a ball joint adapter if you want to keep the upper control arms on your Scamp. You'll need the lower ball joints for a 73-76 A body.