Finding Life Insurance Policy of Deceased Ex-husbanc

My ex-husband has died and he supposedly had a life ins. policy with me as the beneficiary, was from the 1970's. I don't have any idea what ins. company it might be or the amount or if its nothing, he was remarried 5 times and his last wife is unwilling to tell our 2 boys anything. I don't want to spend alot of money finding out and perhaps its not even good or true but if it is I would like to know, we have 2 boys that could share the moneys.. Thanks