Yes, dimension not listed can be accepted if agreed between manufacturer and purchaser,if they are not by pipe fabrication and their design respect all the applicable requirements of the Standard. See paragraph 1.2 of ANSI. But in the market is very difficult found fittings with sizes not listed...
It is standard practice to do this both in the stockist yard and in the field during construction. In 38 year of activity as engineer, never i have had this comment from client.
However, the only problem that i can understand could be related to the original certification,that stated different...
for diesel carbon steel can be used:API 5L or A106 for pipe,A105 for forged fittings/valves/flanges,A234WPB for butt weld fittings,A216 WBC for cast components
for steam you can use the same material, bat the temperature shall be limited at 427 C max. Over Carbon moly steel or low alloy steel...
