The answer? Some liberties shall be taken.
That's definitely going to be the name of the game. The Prototype FGE cars were pretty rare so unlikely to ever be seen in N scale.
8' Superior is what you are looking for, MT makes a drop in replacement.
https://www.micro-trains.com/8-superior-doors-for-50-cars-12-ea-1093-49920916I would renumber it to something in the 5001-5015 series.
and maybe experiment with a fade coat/filter to see if you can pastel up that navy blue a little bit, add COTS and ACI labels, put it in gypsum board service and call it good to go!
The Red car is still perplexing, that shot of 5026 (In Blue/Yellow as Mark suggested) is the only shot of that series I've found.
I did read a couple references that mentioned a solid red scheme used on 5016-5030 at some point so we rest with probably possibly maybe
For a road with basically no boxcars, FEC sure didn't make it easy!
