They don't actually make pans for the rear of the 63-66, as far as I've been able to find out. I bought a set from Rick (Laysons) and I actually got pans marked for a 67-7?...both front and rear...with an explaination that that would have to be trimmed to fit....at Carlisle Kramer had a front pan actually marked (and looking proper) for the 3-6 and told me that the rear pans aren't being popped at the present time. Goodmark has been promising these for a few years now...I haven't installed mine yet but have test fitted and the 67-up pans will work with some mod's, but doesn't look difficult....I can get some pictures this weekend of the pan and the test fit if you'd like....
Dave