I added a 38 gallon fuel tank to the rear of my 1992 E350 460\7.5 E4OD 138WB extended van where the spare tire mount is-was. The fill inlet is 2.25" w a 3/4" fill vent.
Anyone that has done this what are you using for a fill neck and door to cover it? I can adapt the hose size if need be just...