I think Mr. Gasket has a bracket to mount your alternator to headers. It'll put it in the same location it's in now.I could be wrong about who makes it,but it should be easy to find.I used one a while back on a '55 chevy,and I found it on the chrome accessories board at the local parts store.(Actually,the one I got was for a generator but it was easy to make it work with the alternator.)
Speed