So, looking through the book, I came across these three cars.
Project 1 - ACF Pressureaide Covered Hopper
The first is the ACF 4-Bay 5,250 CuFt Pressureaide Covered Hopper. These, of course, are manufactured by Atlas and are readily available on eBay. I always liked these back in my day as a HO (Scale). These would be easy to reproduce with the Microscale #60-19 Rock Island Freight Car - Assorted Block Lettering decals. It's just like decalling a sand hopper, but bigger!
The ROCK had a total of 12 of these cars (RI 13988 through RI 13999). I believe I will construct three of these cars for the layout.
Either one of these would be a good starting point.
Even this one with the patch would be an interesting twist.
Microscale 60-19 Freight Cars - Assorted Black Lettering Decals
Project 2 - Rock Island 53' Bulkhead Flat Car
The second project is a 53' Bulkhead Flat Car. The ROCK assembled their own flat cars through 1958 from components supplied by others. The series I will model will be the 91800-91811 numbers. I will use the Athearn GSC Bulkhead Flat car as a starting point. Again, I could use the same decal sheet #60-19 for the lettering on these cars as well. I think I will construct three of these cars.
Project 3 - Rock Island Steel 52'6" Gondola
The third project I would like to try is a basic 52' Rock Island Gondola. I already have some Trainworx Rock Island Gondolas that are similar, but have the speed lettering. I would take a brown Trainworx gondola, remove the existing lettering and replace with the Rock Island block lettering. By the way, I have always been a fan of the block lettering. I have no idea why as it is so basic, but I like it.
I figure I would just use a TrainWorx gon and remove the existing lettering and replace with the Rock Island block lettering (using the same Microscale 60-19 decals from above). I think I will construct one or two of these cars.