McBain's Lady, Lady, I Did It! is dedicated to Henry Morrison. A good story I've found about Henry is from Lawrence Block who recounts their time at the Scott Meredith agency and MANHUNT magazine here.
Henry Morrison, McBain's dedicatee, was an important part of the Scott Meredith agency. As with Evan Hunter, whose name was changed from Sal Lombino which was considered to sound too "Ethnic", Morrison was born Henry Moskowitz & changed it at Meredith's request.
There's more detail about Morrison, Meredith and the mysterious 'black box' pulp/porn publishing phenomenon in this article. By all accounts Henry Morrison was a much respected member of the agency.
Although I can't find an official up-to-date website, it appears Henry Morrison is still a literary agent having founded his own agency, Henry Morrison Inc., in 1965. It seems he notably handled Robert Ludlum - you may spot Henry's name in the credits of the Bourne movies as Executive producer!