Welcome to the forum!
You may need to draw a plan yourself so as to ensure that it will work with the barrel and lock you want to use.
You can find images of originals if you will search for the following:
"antique dragoon flintlock pistol image"
and
"antique dragoon percussion pistol image"
Both of these searches should pull up several images that could be used for drawing up plans.
Images like that are usually from auction house listings. If you will click on the image, you can usually also go to the original site, and some of the sites provide an option for enlarging the view of the images. Some of the auction house sites don't allow you to directly save images, but you can do a screen save (Alt + PrtScn) and then drop the screen saves into a Word file. Save the URL links, as well, so that you can go back to the site if you want to. I save images like this quite often. I learned to do this after I discovered that some of the auction houses only leave their photos up for a short while. I learned that if I wanted to save images from an auction house listing, it was best to go ahead and get them when I found them, otherwise they might not be there the next time I wanted to see them.
