The Grave of Truth by Evelyn Anthony

It was the dream Max had been having since the war. The dream of those horrifying, final moments in the Fuhrer's Bunker - images of that night of terror, of the brutally beaten, dying man and his last desperate words; dreams of a past from which Max can't escape.
Suddenly, it starts all over again - but it is no longer a dream. And now Max finds himself caught in a chilling search for Hitler's last legacy...
The story of a deadly race to discover the Fuhrer's final evil bequest to mankind.