Highschool65, I have the 1261 (Pertronix l) model installed on my 66' - 200cid engine with an orginal Ford Load-A-Matic distributor, and it works fine! I did have to file a little bit off of the Perronix base plate to set the proper air-gap, but I have read where a few other people had to do the same thing! A printed sheet that I have from Pertronix's website does list Model # 1261 (Model #91261 is the Ignitor ll part #) for all 1949 to 1974 6's (excluding the V-6's) that have the "Motorcraft" distributors. Model # 1266 (or #91266 for the Ignitor ll) is suppose to be for 1963 to 1967 Ford sixes (except the V-6's) that have the "Holley" distributors!
Hope this helps, Jim