I do a lot of scratch building, mainly pre war types and find most of the information from the net, it takes a bit of searching but I usually find enough information to allow me to build the model. I have written to a lot of museums but for some reason they are very reluctant to help. Some aeroplanes I would love to scratch build are lacking any good reference material so they have to be shelved but in most cases you will find what you need. Also asking questions here on the forum will reveal lots of info, many of our members have excellent libraries.
Des.