Is it possible to hook up a tach to this alternator?
That looks like an older Mitsubishi 35A externally regulated alt. The terminals are generally:
E= Neg/Ground (for the brush)
F= Field = F (other brush lead)
N = Stator Tap / AC Pulse / Tach
A = 12V+ / B+
B = B+ to large battery cable
Unlabeled Stud = Case Ground