63-66 brake upgrade options

You can. I upgraded my 64 to a 67 dual reservoir disc brake master cylinder and disc brake proportioning valve, because I have a set of factory small bolt pattern disc brakes I rebuilt for it some time ago. I have yet to install them, but it stops very well just like it is. You will have to at least go to 14" wheels for disc brakes, but if you stay with the drums, you can retain then 13s. You don't have to use the disc brake master cylinder like I did. You can just use the drum brake dual reservoir master cylinder. Get one for the 67 model and you should be fine. Of course, you'll need the distribution block for the dual reservoir master cylinder and the extra line. It's a very easy upgrade.