I changed the drivers side frame rail and it fit pretty good but the sway bar bracket is different than the original and was not in the correct spot. I had to drill the spot welds and weld on the original bracket
Like the first reviewer, the sway bar bracket is located too far back for a 1966 also (about 1-1/4"). The bracket itself is different than my original, with the sway bar holes about 7/8" closer to frame rail... not sure if that will be a problem until I go to mount the sway bar. The frame rail itself appears to fit well. everything else looks as though it should work. Plan on taking off the bracket and using your stock bracket if you can salvage it or rewelding this bracket on in the correct location. Maybe it fits a 1967 or later model better?
The swaybar/core support brackets are welded 1.5 inches to far back for 64 1/2. If used as recieved your original core support brackets don't rest on front radiator support far enough. Brackets have to be removed and moved forward but before you do that there is an extra 1 1/4 diameter hole that need to be filled or part of the brakcket falls right in the center of the hole.