found: Hallmark summer theater. The legend of Josiah Blow [MP] 1952:(cast, Biff McGuire)
found: Notable names in the American theater:p. 970-971 (Biff McGuire; b. 10/25/1927; actor and playwright; same as William Joseph McGuire, Jr.)
found: Hollywood reporter, Apr. 3, 2021(William "Biff" McGuire; actor with a career spanning 70 years; born Oct. 25, 1926, New Haven, CT; began acting while stationed in England during World War II; had numerous film appearances as well as extensive theater roles and some television roles; no details about his death were released)
found: Wikipedia, Aug. 11, 2021(Biff McGuire; William "Biff" McGuire, American actor; born Oct. 25, 1926, New Haven, CT; died Mar. 9, 2021, citing SAG-AFTRA (Spring 2021))