what the hell is a reptile ballast? if you mean the aluminum dome fixture with the black plastic socket then no. you cant use them. plus you will still need a 70 watt ballast (which is the transformer that powers the bulb). ive never seen 75watt HID lights..
if you want to use just the aluminum dome as a reflector it would be okay for up to 150 watts, but the platic sockets they come with have to go.