I'm not 100% sure of what thought path your going down, however this may help.
You obviously have the original glass, hence the original scan, hence access to the original overall dimensions.
Accurately measure the original glass overall width and height. If Tom's file does not include the overall main black base underlay, measure the overall width of the artwork instead (which would be the outer light grey pin-striping I would imagine)
Open up Tom's vector of the artwork in AI. Then go to the uper menu bars and go EDIT..PREFERENCES..GENERAL. Make sure you check the box next to 'Scale Stroked and Effects', in case this is relevant to the file parameters. Also go to 'UNITS & DISPLAY PERFORMANCE' and select the size units you prefer to use (I use mm's being an Aussie and all

)
Then make sure non of your relevant layers are locked (little padlock next to them should NOT be there, in the layer window.) Then go CTRL+A (select-all command).
Click on the 'Scale too'l in the tools menu (under the pencil tool, just hover over the top to see what it is)
Go back to the upper menu bar and click WINDOW.. and make sure the 'Transform Window' is checked. Within this window, make sure the little chain link is clicked, which in turn links the W:(width) and H:(height) to keep the files original aspect ratio.
Then type in the original glass or artwork (whatever is relevant) width dimension in the W: field.....and press enter...DONE
The file should have scaled correctly, automatically keeping the original aspect ratio. Because Tom compiled the file from an original scan, all the size ratios should be correct.
Good Luck. Hope this helped.