Hey CAS, where did you find a DC-3 template? i have scoured the internet and cant find one!
Meko, here is the one I used. Only I flipped it to face the other way, retracted the landing gear, erased the text labels and did some editing on the lines printed along the fuselage to make them appear less bold and prominent. I also added a few details such as the engine exhausts etc.

I also struggled at first to find any vintage templates but then Matias gave me the following advice in an earlier post. He recommended searching the aircraft name/designation followed by either drawing, line drawing, three way drawing or template (For example: "DC-3 drawing" or "DC-3 line drawing"). More often than not I found more than enough templates of various sorts for most aircraft. I also had some luck when using the word sketch together with the aircraft name (For example: "DC-3 sketch"). You see... the thing with all the ones I found are that they are not the Jetabout type templates that are designed with livery design in mind and nearly all of them require some editing to make them perfect in my opinion. Although I'm particularly pedantic so it might not matter to others really.
But I must add that for some aircraft you can search your holy, best, but off and you wont find anything decent! Like the Convair 340/440 series. Actually... I am currently in the process of tracing my own CV440 template off a photograph taken directly from the side. Now that... is a very, very annoying and terribly tedious job!