It's a fun myth but it's not true. The SRBs for the Space Shuttle were designed to satisfy their mission criteria. While any similarity between US rail widths today and Roman roads is due more to happenstance than a direct result.
Hey there fellow Texan. If you're planning on releasing it on a permissive license I'll help with what I can. Do you already have high quality scans of the pages you could upload to GitHub?
https://www.snopes.com/fact-check/railroad-gauge-chariots/