how would you find out where a construction foreman who worked on the
movie Sounder in 1972 is now?

Since there is no name given, here are the steps.
Get the name from the credits. Also, get the production compnay name.
A simple entry of the persons name in Google with quotes, like "Bob
Smith" may get you the info you request. However, if not, call the
production company. But produciton companies are often open and
closed. So, then try the (Setworkers)Union, if he is a member, they
will have info. They may not give it to you, but they will have it.

I hope something in here helped.