While searching the web for lighting parts, I came on a site that has many things needed for a resto-mod.
In their catalog, besides all sorts of parts, they also have many "How-To" sections, one of which I'm going to use on my project.
The catalog is available at www.carbuildersolutions.com.
I also subscribe to Skill Shack (online automotive tutorials) and Practical Classics (UK Magazine).
Give them a try and if you have other sources, add them to this string.