I’m actually a little surprised the HemiDenny Kit costs more. That was always a big selling point was it being the more budget friendly between the Alterkation and the HDK.
now to your question, no you can’t use the same exact set from your 73-76 A body kit. However, you can contact wilwood and get the correct caliber brackets to bolt the calibers to the Mustang II spindles of the Alterkation. Most wilwood kits use the same calibers across multiple vehicles. May need the rotor hub swapped too as the mustang II bearing sizes are different