Vehicle and product modelers here often start the same way: gather length, width, height, and wheelbase, then scale photos or drawings to those numbers.
I packaged that first step. **mmboard** is a small original Python CLI. You drop in your own photos or drawings plus a `measurements.txt`. It writes `board.html` with those millimetres labeled. It does not live inside Blender and it does not measure a mesh.
$12 on itch. Sample in the zip is original schematics, not scraped blueprints.
Happy to answer how the `measurements.txt` is shaped if useful.