Chiliman, are you asking about the bottom bolt to align the fan belt? Unfortunately I don't have an answer for you, just trying to clarify your question.
If you are looking for a bracket like 160B suggested, I have used (with a little tweaking) a tensioner bracket from a SBC. Much cheaper and easy to find.
I make my own because I use a second hand alternator bought from a wrecking yard. The shape of the bracket depends on which alternator you are using because the mounts vary from car to car. If you don't have the facilities to make one, maybe someone you know has.
The OP was asking about an adjustable mount for the BOTTOM of the alternator so he could align the belt.
I don't think there is such a thing. As a solution, see my earlier post.
I used the A10001ADJ bracket kit from Mike’s A Ford Able.It’s not cheap but is well made and fully adjustable. I used it to mount a small 1wire Denso alt on my A.