charging system

1974 Midget, 1275 engine, negative ground, alternator project.
We need help troubleshooting.  We've charged battery, cleaned all
terminals, changed alternator. Battery reads only 12 volts when running--
no charging happening. Alternator light does not come on when key is on
and engine is not running. Any ideas on how to check alternator output and
get battery to charge. Thanks.
Dick B. in NH