Been out of town for a week,....
I've got a wire going from tach to coil as you described and the tach will work. However it seems to be reading double the actual rpm's. For example, at idle the tach is reading close to 2000. I may have tach issues because it does seem to flicker, but I was happy just to see the needle move at the time.
Also, does anyone have a part number for an alternator replacement that might be local for me. i.e. Autozone, Advanced Auto, Pep Boys, etc.