Ancestry has long had the largest collection of genealogy data online being an early leader in subscription based genealogy. Because of its extensive census images and indices, and its World War 1 Draft Cards, it has the best collection at this time too. Its census images presently cover all available federal US records, and contains extensive census images from Canada, UK, Scotland, and Germany. This is a subscription based service, however you can access the databases for the next 14 days for free by using their Free Trial at Ancestry offer.
I started with a full list of Great Western steam locomotives that were included on a spotter's list of 1944 as still operating. I've also now added data from a full list of named LMS steam locomotives from a 1943 spotter's list, more from a full list of SR steam locomotives from a 1945 spotter's list, even more from a full list of LNER locomotives from a 1943 spotter's list, and I've filled in a few more details for some of the existing records here. I still have spotter's lists for Ireland from the same era to add, and I'm going back through my reference library to find and add more data.