I think part of the confusion is that too many internet sources mention a Springfield 1903A3 when actually none of the A3 models were made by Springfield, as they were too busy making the M1 Garand. Hatcher's Notebook has a pretty good description of the changes and I think you got it right. Lots of little details changed and a lot of parts do interchange. Most of the changes were to speed production and reduce costs. Thanks for the input.