Les Sittler asked:
"The only remaining question I have is, you previously referenced the Don Valentine door and one-half kit- was this to retrofit the steel end cars back before they were rebuilt to 6’ doors or what was the purpose?"
The Standard Steel Car Co. (one of Don's New England Rail Service product lines) auxiliary door (conversion parts only, NOT a full kit) is for a kitbash of the Accurail SS boxcar into GTW automobile boxcars first documented by Richard Hendrickson in the April 1993 issue of Railmodel Journal (page 13):
Richard did this first kitbash by cutting up a second model for the auxiliary door - these conversion parts greatly facilitate this project.
Realize that you're new here, but a lot of your questions on the Accurail cars have been discussed before on this list. You might want to give the list archives a search first. The search engine isn't terribly great, but it stands a good chance to turn up answers to previous questions. In this case, several list members have done this project in the past and posted photos and other information.