Technically yes, you could modify the OEM alternator bracket but it would be difficult to know exactly how much it needs to be machined. Also, you'd also need the JRSC crank pulley and a different supercharger pulley.
D-serious has the measurements for everything. He could probably have the crank pulley, the lower alternator bracket, and the supercharger pulley machined for you but I don't know how busy he is or how much it would cost.
Your best bet is going to be to try to get the supercharger installed as-is. Otherwise you're probably looking at several hundred dollars in additional parts and who knows how long of a wait.
The pic is from the internet. Not the one I have. Same manifold but I do have 3 rib pulley 3 rib crank pulley and spacer for alternator. All im missing is the lower bracket. I wonder if moss motors carries it.