"Now to find something that contradicts it."
http://www.vectorsite.net/avvulcan_2.html
"Some sources claim that Vulcan B.2s that were modified to carry Blue Steel were given the designation of "Vulcan B.2A", but others say that it was the Olympus 301-powered machines that had this designation, and still others say the "B.2A" designation is a fiction."
Many of the books and magazines also give the B2A designation for the 301 engined aircraft.