If you are referring to the round hood style rear fenders (32R/ 32E, 33R/ 33E, 34R/34E), they would only fit if you modify the sheetmetal underneath. The original 65-67 fender support runs horizontally front the tower to the rear of the seat pan.
The easiest thing to do is find a 62-64 Ranger center column. That wasn't an option for me because they don't turn up here in NC very often. Of course that requires using a different hood as well...
I added round fenders on my son's 1967 Ranger but alot of fabrication was involved. The toolbox for round fenders is a couple inches shorter so I not only had to cut the original 67 support to allow for the toolbox to mount on the transmission, but I also had to cut and weld an angle into the center to match the round fender tool box.
You could just cut the original fender support to allow the round fender toolbox to fit, but it will be a couple inches higher than the top of the toolbox.