"Since I bought NSC NYC decals there’s an IHB subject on the sheet I’d like to do. I’ve found a photo of a car with 5/5 ends. Did Branchline offer this end in their 40’ boxcar series?"
They did not...but why use the Branchline model as a starting point? What's wrong with the Intermountain 10 ft 6 in IH Modified 1937 AAR Boxcar model? Despite the 1944 build date, IHB 10600-10699 (Lot 730-B) were built to the earlier design. See Ed Hawkins' spreadsheet for details.